Collatz-problem; approximation 2S to 3N
a large scale view;  N = 1..1038 ; a hullcurve N=1…10250
and some more data up to N~102400


 

1.        A large-scale view into the distance of 3N and the next perfect power of 2

1.1.     The problem

In the investigation of the possibility of 1-cycles under the Collatz-iteration (see [1]), we find, that the length N of such a hypothetic cycle and the distance of 3N to the next greater power 2S is a crucial relation. Here S is defined such that 2S > 3N and more precisely, such that

                S = ceil (N log(3)/log(2) )

which, in relation to the collatz-problem means: N is the number of operations 3x+1, and S is the number of x/2-operations if we consider the 1-cycle (or "primitive-loop" in my older formulation). Although that problem of the existence of an 1-cycle was solved to the negative by Ray Steiner already in 1977 using a result of G. Rhin, the bound, which occurs there seems very rough. So to get an own impression of the behaviour of the approximability of 2S to 3N (where N is given) I produced data using the arbitrary-precision software Pari/GP.

We are interested in the relative value of that distance, and use the log, because the values of the original function cannot be used with a computer if N itself goes to hundreds or thousand digits.

1.2.     The function f(N) under consideration and the hullcurve of moving minima

So first we look at

                f(N)       = log(2S/3N)
                               = log(2)*(ceil (N log(3)/log(2) ) – N log(3)/log(2))
                               = log(2)*( 1 - frac (N log(3)/log(2) ) )

 

First few values for f(N) are

                log(4/3) = log(1.333..), log(16/9)=log(1.7777…), log(32/27)~log(1.185[185]…)

                               (for more values see table in appendix)

The values f(N) range from 0 to log(2)~0.69314 (exclusive the bounds); a "good" approximation (small relative distance) is f(N) near zero, a "bad" approximation is f(N) near log(2). Also "good" approximations improve with increasing N, but we don't have an easy relation of N to that measure of quality of approximation. So in plot 2 I show a trend, how it appears in a very large scale view for N=1 to 1038 .

1.3.     First impression and the idea of a hullcurve (or envelope)

But before the plot with the trend another, more obvious plot to introduce into the idea of envelope. Here I used N=1 to N=800 and the function-values for each N.

Plot 1: Plot of approximants f(N) for some small N

 

We see a clear regularity ; the apparent antidiagonals of slope ~-45°, for instance, occur, if we increase N in steps by 12 beginning at N=5.

However, if we look at the points nearest the x-axis (y~0), then we see that there is also another cyclicitiness overlaid: we have a very low point at N=41, then the next lower points follow in steps of 53 up to N=306, where the rhythm breaks such that at N=306+53 we have a very high point instead.

This general behave is simply due to modularity of f(N) mod(log(2)). However, it does not lead to exact periodicity of the distances. The reason for this is the irrationality of the ratio log(3)/log(2) and N.

Anyway, for the analysis of the Collatz-problem, namely the discussion of the "primitive loop" (or "1-cycle") we are interested in the cases of best approximations. We may say, that cycles are "more likely" for length N, if the distance-measure f(N) is small, or near zero. Well: "likeliness" is not really a correct notion for the cycle-discussion, but it gives here an idea, that we are interested in the sharpest approximations depending on N.

So we define a lower envelope for the f(N)-function by connecting the moving minima of the points when increasing N; in the above plot it is indicated by the blue line.

1.4.     The lower envelope for f(N)

We are then interested in the characteristic of that envelope.

In the following plot I draw that envelope, whose points were determined using the continued-fraction-representation of log(3)/log(2). That representation gives the points N at which minimal values f(N) occur. That method allows to find relevant N up to N=1038 and its values f(N) in a few seconds, so we get enough points for a good overview. Because we deal with huge values of N and also very small values of f(N) I used a logarithmic scale for both values. (For visual comparision I also inserted sample points for some N which are not on the envelope)

Plot 2:

Surprisingly the general tendency of the lower envelope envlow is linear in this log-scales. This information is new to me; I didn't come across a linear ratio of that logarithms before (in [1] I had some logarithmic/polynomial guess bases on much less N).

The long-scale relation between N and envlow(f(N)) is then, using the above equation for the trend, in some different ways of expression:

                envlow (log10(f(N)))                       ~ –0.994 log10(N) + 0.022
                envlow (log(f(N)))                          ~ – 0.994 log(N) + 0.050657
                envlow ( f(N) )                                   ~ 1.05196 * N-0.994
                envlow (2S/3N )                                                ~ 3 2.863/N^0.994
                envlow (2S )                                        ~ 3 N+2.863/N^0.994

 

Note: this does not help for the general cycle. The trend in this formulation is also very raw and rather useless for the actual computation of the upperbound for the smallest member of the general cycle. Such computation should be made on the base of the original computation for each N. In table 2.2 I give some example data for cycle-lengthes N=1 to N=100 instead. That table shows the lower bound for a1 to make a cycle impossible, or said differently: the smallest member of a general cycle must be smaller than the given bound (but all of these small values a are easily checked empirically and none is member of a cycle, so cycles of the indicated lengthes cannot exist. For instance, if a1=5 is given, no cycle at all is possible – solely on the discussed approximation argument).

 

 

1.5.     More values and another hullcurve

I proceeded using more terms for the hullcurve up to 1600 coordinates which means I arrived at N~10^250. Setting precision of computation in Pari/GP to 15000 gives about 14500 entries for the continued fraction of log(3)/log(2). Building the list of convergents gives about 80000 values for N, which gives the coordinates for the hullcurve.

To finally compute with all these values I had then to reduce the precision to 5000 digits (because of memory management) and could effectively check the coordinates up to N~ 10^2848 distributed in about 25000 entries in that table of convergents. Because log(N) seems in the great overview nearly linear with log(f(N)) I computed the difference of that values log10(N) – (-log10(f(N))) = log10(N*log(2^S/3^N)) . That differences were in a very near range of about –4 to +5 . However, also here we find nonconstant bounds, so there is again the need of a greater overview: to look at a hullcurve connecting that progressive extrema. Here is the Pari/GP-program and then the few coordinates of that hullcurve.

 

fmt(15000,12)
cfl  = cf_convergentslist(log(3)/log(2));
            \\ length(cfl)
            \\ %2414 = 14569               \\ number of coefficients of cont. frac

cf_xopt_chklae( cfl )      \\ check length when list of convergents were expanded to all N with diminuishing intervals
            \\  %2415 = 82099              \\ length of that list, this is too long for current memory allocation!

NList = cf_xopt( cfl , 25000);             \\ create list containing all relevant N
                                           \\ allocated memory allows only to work with about 25000 entries
            \\ VE(NList,5)                         \\ do a short check , show the first few entries N
            \\ %2417 = [1, 3, 5, 17, 29]~  \\ the first few N (for the exponent of 3^N according to the list of convergents

fmt(5000,12)                               \\ precision may be reduced, but must be >2000 (for instance)
 [lg10=log(10),lg2=log(2),lg3=log(3),ld3=lg3/lg2]  \\ recompute constants with current prec

amin=5;amax=-5;                            \\ loop to find the moving minima of the deviation-function df(N) = log(N) – (-log(f(N))
for(k=1, length( NList) ,
        N = NList [k]; lgN = log(N) ;
        fN = lg2*(1-frac(ld3*N)); lgfN = log(fN) ;
       
        dfN = lgN – (- lgfN) ;
        if( dfN < amin, amin = dfN;                \\ if dfN has new minimal value, register and print values
              print(k," ",lgN/lg10," ",dfN/lg10))  \\ use log to base 10 for more transparent display
    )

Table 1.3: Coordinates for hullcurve characterizing N*f(N) using log10(N * log(2S/3N))

index into list of N

log10(N)

log10(N)–(–log10(f(N)))

1

0.0

-0.541087201293

3

0.698970004336

-0.584058910762

37

5.27997932298

-1.91041044730

542

106.118391607

-2.16096110843

597

114.250602011

-3.14344653731

971

167.420643539

-3.54599907505

1730

272.363973245

-3.67896692796

9591

1407.08628196

-3.84754329367

19795

2234.17531188

-4.07448957185

 

 

 

highest checked index:

 

 

25000

2848.44052764

 

 

According to this, up to N~102848 we have 

                log(2S/3N) > 1/(N*104 )

where it is not yet recognizable, which form (linear, parabolic, logarithmic,…) that hullcurve shows in a even longer scale. (If we use the log10 of log10(N) again, it looks as if we have again a bound roughly linear with that values…)

 

Gottfried Helms,             3'2010  (previous version: 7'2009)

 

for a overview of the related cycle-discussion ("primitive loop") see:

[1]                 "cycles in the collatz-iteration",
G. Helms, 2006-2008
http://go.helms-net.de/math/collatz/Collatz061102.pdf


2.        Appendix

How to read the following table:

N

f(N)=log(2^S/3^N)

log10(N)

log10(f(N))

3^N

3^N*exp(f(N))=2^S

length of the cycle (T()-transformations)= 1

0.287682072452

0.000000

-0.541087201293

3^1 =    3

    3*exp(f(N))=4

length of the cycle (T()-transformations)= 3

0.169899036795

0.477121254720

-0.769809083259

3^3 =  27

  27*exp(f(N))=32

length of the cycle (T()-transformations)= 5

0.0521160011390

0.698970004336

-1.28302891510

3^5 =243

243*exp(f(N))=256

17

0.0385649677607

1.23044892138

-1.41380702736

 

2.1.     Data for graph of envelope:

N

f(N)

log10(N)

log10(f(N))

1

0.287682072452

0.000000

-0.541087201293

3

0.169899036795

0.477121254720

-0.769809083259

5

0.0521160011390

0.698970004336

-1.28302891510

17

0.0385649677607

1.23044892138

-1.41380702736

29

0.0250139343823

1.46239799790

-1.60181799375

41

0.0114629010039

1.61278385672

-1.94070545824

94

0.00937476862954

1.97312785360

-2.02803944191

147

0.00728663625513

2.16731733475

-2.13747290968

200

0.00519850388072

2.30102999566

-2.28412162749

253

0.00311037150632

2.40312052118

-2.50718773525

306

0.00102223913191

2.48572142648

-2.99044749802

971

0.000978585021321

2.98721922991

-3.00940143604

1636

0.000934930910732

3.21378329934

-3.02922048132

2301

0.000891276800144

3.36191661867

-3.04998739798

2966

0.000847622689555

3.47217114669

-3.07179742641

3631

0.000803968578966

3.56002624891

-3.09476092420

4296

0.000760314468378

3.63306427269

-3.11900674504

4961

0.000716660357789

3.69556922704

-3.14468661795

5626

0.000673006247200

3.75019972783

-3.17198090441

6291

0.000629352136612

3.79871968519

-3.20110628906

6956

0.000585698026023

3.84235957333

-3.23232623967

7621

0.000542043915434

3.88201196163

-3.26596552627

8286

0.000498389804846

3.91834492896

-3.30243085027

8951

0.000454735694257

3.95187155713

-3.34224095472

9616

0.000411081583668

3.98299445466

-3.38607197905

10281

0.000367427473080

4.01203535915

-3.43482837399

10946

0.000323773362491

4.03925544381

-3.48975888442

11611

0.000280119251902

4.06486962506

-3.55265704217

12276

0.000236465141314

4.08905687976

-3.62623287205

12941

0.000192811030725

4.11196783721

-3.71486812372

13606

0.000149156920136

4.13373046662

-3.82635659274

14271

0.000105502809548

4.15445440614

-3.97673597492

14936

0.0000618486989592

4.17423430494

-4.20866943170

15601

0.0000181945883705

4.19315243685

-4.74005776533

47468

0.0000109296545229

4.67640093369

-4.96139356551

79335

0.00000366472067521

4.89946482607

-5.43595912166

190537

0.0000000645075027718

5.27997932298

-7.19038977028

10781274

0.0000000122069827808

7.03267008353

-7.91339166804

64497107

0.00000000873439391323

7.80954023491

-8.05876722569

118212940

0.00000000526180504562

8.07266501853

-8.27886524693

171928773

0.00000000178921617802

8.23534856377

-8.74733718361

397573379

1.05843488432E-10

8.59941729690

-9.97533585493

6586818670

1.01231253207E-11

9.81867570782

-10.9946853867

72057431991

5.51089009577E-12

10.8576787805

-11.2587782501

137528045312

8.98654870862E-13

11.1383912704

-12.0464070674

890638885193

7.79694000263E-13

11.9497016525

-12.1080758077

1643749725074

6.60733129664E-13

12.2158356932

-12.1799739168

2396860564955

5.41772259065E-13

12.3796427701

-12.2661832364

3149971404836

4.22811388467E-13

12.4983066113

-12.3738533234

3903082244717

3.03850517868E-13

12.5914077027

-12.5173400191

4656193084598

1.84889647269E-13

12.6680309815

-12.7330874061

5409303924479

6.59287766701E-14

12.7331413832

-13.1809249827

11571718688839

1.28966827413E-14

13.0633978673

-13.8895219837

64021008208555

1.14513197778E-14

13.8063225092

-13.9411444575

116470297728271

1.00059568144E-14

14.0662151856

-13.9997413759

168919587247987

8.56059385088E-15

14.2276800116

-14.0674961071

221368876767703

7.11523088740E-15

14.3451165614

-14.1478110026

273818166287419

5.66986792391E-15

14.4374622577

-14.2464270576

326267455807135

4.22450496043E-15

14.5135737564

-14.3742241756

378716745326851

2.77914199695E-15

14.5783145083

-14.5560892629

431166034846567

1.33377903347E-15

14.6346445419

-14.8749161138

914781359212850

1.22219510347E-15

14.9613173063

-14.9128594605

1398396683579133

1.11061117346E-15

15.1456303853

-14.9544379616

1882012007945416

9.99027243451E-16

15.2746223901

-15.0004226684

2365627332311699

8.87443313444E-16

15.3739463294

-15.0518593785

2849242656677982

7.75859383436E-16

15.4547294376

-15.1102169830

3332857981044265

6.64275453429E-16

15.5228168080

-15.1776517955

3816473305410548

5.52691523421E-16

15.5816622290

-15.2575171961

4300088629776831

4.41107593414E-16

15.6334774070

-15.3554554660

4783703954143114

3.29523663407E-16

15.6797642949

-15.4821133929

5267319278509397

2.17939733399E-16

15.7215896439

-15.6616635847

5750934602875680

1.06355803392E-16

15.7597384290

-15.9732388075

11985484530117643

1.01127676776E-16

16.0786555957

-15.9951299698

18220034457359606

9.58995501609E-17

16.2605491940

-16.0181834300

24454584384601569

9.06714235454E-17

16.3883602862

-16.0425295658

30689134311843532

8.54432969300E-17

16.4869846379

-16.0683220022

36923684239085495

8.02151703145E-17

16.5673050283

-16.0957434901

43158234166327458

7.49870436990E-17

16.6350636671

-16.1250137678

49392784093569421

6.97589170835E-17

16.6936635065

-16.1564002699

55627334020811384

6.45307904680E-17

16.7452882466

-16.1902330150

61861883948053347

5.93026638525E-17

16.7914231419

-16.2269257979

68096433875295310

5.40745372370E-17

16.8331243691

-16.2670071885

74330983802537273

4.88464106215E-17

16.8711698809

-16.3111673440

80565533729779236

4.36182840061E-17

16.9061492886

-16.3603314241

86800083657021199

3.83901573906E-17

16.9385201437

-16.4157801074

93034633584263162

3.31620307751E-17

16.9686446515

-16.4793588820

99269183511505125

2.79339041596E-17

16.9968144498

-16.5538683612

105503733438747088

2.27057775441E-17

17.0232678282

-16.6438636214

111738283365989051

1.74776509286E-17

17.0482019950

-16.7575169388

117972833293231014

1.22495243131E-17

17.0717820098

-16.9118807760

124207383220472977

7.02139769766E-18

17.0941474122

-17.1535764275

130441933147714940

1.79327108217E-18

17.1154172264

-17.7463540548

397560349370386783

1.51686631025E-19

17.5994030636

-18.8190526943

4640282259296926456

2.69684901278E-20

18.6665443986

-19.5691433675

27444133206411171953

1.01243097420E-20

19.4384495186

-19.9946345766

77692117359936589403

3.40443909807E-21

19.8903769575

-20.4679544305

205632218873398596256

8.90075522457E-23

20.3130911618

-22.0505731421

7941964418702608664581

6.68554395133E-23

21.8999279370

-22.1748632518

15678296618531818732906

4.47033267809E-23

22.1952988766

-22.3496601559

23414628818361028801231

2.25512140485E-23

22.3694872775

-22.6468300728

31150961018190238869556

3.99101316135E-25

22.4934714493

-24.3989168400

1752190149218482586763461

1.97560971162E-25

24.2435812344

-24.7042988476

5225419486637257521420827

1.93581597351E-25

24.7181211605

-24.7131359309

8698648824056032456078193

1.89602223540E-25

24.9394517982

-24.7221565738

12171878161474807390735559

1.85622849729E-25

25.0853575965

-24.7313685642

15645107498893582325392925

1.81643475919E-25

25.1943785516

-24.7407801961

19118336836312357260050291

1.77664102108E-25

25.2814501090

-24.7504003146

22591566173731132194707657

1.73684728297E-25

25.3539463397

-24.7602383664

26064795511149907129365023

1.69705354486E-25

25.4160543221

-24.7703044548

29538024848568682064022389

1.65725980675E-25

25.4703814515

-24.7806094024

33011254185987456998679755

1.61746606865E-25

25.5186620247

-24.7911648212

36484483523406231933337121

1.57767233054E-25

25.5621082027

-24.8019831911

39957712860825006867994487

1.53787859243E-25

25.6016006217

-24.8130779485

43430942198243781802651853

1.49808485432E-25

25.6377992511

-24.8244635867

46904171535662556737309219

1.45829111621E-25

25.6712114695

-24.8361557699

50377400873081331671966585

1.41849737810E-25

25.7022357571

-24.8481714626

53850630210500106606623951

1.37870364000E-25

25.7311907902

-24.8605290778

57323859547918881541281317

1.33890990189E-25

25.7583354232

-24.8732486466

60797088885337656475938683

1.29911616378E-25

25.7838827847

-24.8863520136

64270318222756431410596049

1.25932242567E-25

25.8080104502

-24.8998630628

67743547560175206345253415

1.21952868756E-25

25.8308679358

-24.9138079791

71216776897593981279910781

1.17973494945E-25

25.8525823146

-24.9282155545

74690006235012756214568147

1.13994121135E-25

25.8732624957

-24.9431175454

78163235572431531149225513

1.10014747324E-25

25.8930025287

-24.9585490944

81636464909850306083882879

1.06035373513E-25

25.9118841903

-24.9745492295

85109694247269081018540245

1.02055999702E-25

25.9299790303

-24.9911614587

88582923584687855953197611

9.80766258914E-26

25.9473500096

-25.0084344835

92056152922106630887854977

9.40972520806E-26

25.9640528215

-25.0264230591

95529382259525405822512343

9.01178782697E-26

25.9801369694

-25.0451890418

99002611596944180757169709

8.61385044589E-26

25.9956466510

-25.0648026728

102475840934362955691827075

8.21591306481E-26

26.0106214909

-25.0853441648

105949070271781730626484441

7.81797568373E-26

26.0250971500

-25.1069056847

109422299609200505561141807

7.42003830264E-26

26.0391058376

-25.1295938529

112895528946619280495799173

7.02210092156E-26

26.0526767427

-25.1535329331

116368758284038055430456539

6.62416354048E-26

26.0658364002

-25.1788689540

119841987621456830365113905

6.22622615940E-26

26.0786090033

-25.2057751082

123315216958875605299771271

5.82828877832E-26

26.0910166714

-25.2344589381

126788446296294380234428637

5.43035139723E-26

26.1030796799

-25.2651720664

130261675633713155169086003

5.03241401615E-26

26.1148166605

-25.2982236367

133734904971131930103743369

4.63447663507E-26

26.1262447734

-25.3339993030

137208134308550705038400735

4.23653925399E-26

26.1373798590

-25.3729887652

140681363645969479973058101

3.83860187290E-26

26.1482365693

-25.4158269291

144154592983388254907715467

3.44066449182E-26

26.1588284842

-25.4633576745

147627822320807029842372833

3.04272711074E-26

26.1691682135

-25.5167369959

151101051658225804777030199

2.64478972966E-26

26.1792674870

-25.5776088502

154574280995644579711687565

2.24685234858E-26

26.1891372350

-25.6484254662

158047510333063354646344931

1.84891496749E-26

26.1987876589

-25.7330830618

161520739670482129581002297

1.45097758641E-26

26.2082282948

-25.8383392962

164993969007900904515659663

1.05304020533E-26

26.2174680698

-25.9775550470

168467198345319679450317029

6.55102824247E-27

26.2265153535

-26.1836905283

171940427682738454384974395

2.57165443165E-27

26.2353780027

-26.5897873905

347354084702895683704606156

1.16393505247E-27

26.5407724103

-26.9340712526

870121826425948596728844073

9.20150725772E-28

26.9395800628

-27.0361410270

1392889568149001509753081990

6.76366399071E-28

27.1439166858

-27.1698179757

1915657309872054422777319907

4.32582072370E-28

27.2823178212

-27.3639314831

2438425051595107335801557824

1.88797745669E-28

27.3871094115

-27.7240031957

5399617844913267584627353565

1.33811164637E-28

27.7323630239

-27.8735076494

8360810638231427833453149306

7.88245836047E-29

27.9222483873

-28.1033383148

11322003431549588082278945047

2.38380025725E-29

28.0539232822

-28.6227301377

36927203087966924495662630882

1.65274266854E-29

28.5673464149

-28.7817947607

62532402744384260909046316717

9.21685079830E-30

28.7961051163

-29.0354174428

88137602400801597322430002552

1.90627491119E-30

28.9451612323

-29.7198144679

378155609259623725703103696043

3.14523757646E-31

29.5776705468

-30.5023465444

2558951662416564482599295869749

2.95391392334E-31

30.4080620823

-30.5296021641

4739747715573505239495488043455

2.76259027021E-31

30.6757552259

-30.5586835221

6920543768730445996391680217161

2.57126661709E-31

30.8401402197

-30.5898528886

9101339821887386753287872390867

2.37994296396E-31

30.9591053302

-30.6234334508

11282135875044327510184064564573

2.18861931084E-31

31.0523913258

-30.6598297732

13462931928201268267080256738279

1.99729565771E-31

31.1291396499

-30.6995576422

15643727981358209023976448911985

1.80597200459E-31

31.1943402557

-30.7432889862

17824524034515149780872641085691

1.61464835146E-31

31.2510179418

-30.7919220465

20005320087672090537768833259397

1.42332469834E-31

31.3011455045

-30.8466960145

22186116140829031294665025433103

1.23200104521E-31

31.3460812821

-30.9093889237

24366912193985972051561217606809

1.04067739209E-31

31.3868004983

-30.9826838800

26547708247142912808457409780515

8.49353738964E-32

31.4240270362

-31.0709113971

28728504300299853565353601954221

6.58030085840E-32

31.4583130158

-31.1817542495

30909300353456794322249794127927

4.66706432715E-32

31.4900891747

-31.3309562131

33090096406613735079145986301633

2.75382779590E-32

31.5196980325

-31.5600632208

35270892459770675836042178475339

8.40591264657E-33

31.5474164488

-32.0754151275

107993473432468968265022727599723

6.08537262725E-33

32.0333975098

-32.2157128233

180716054405167260694003276724107

3.76483260793E-33

32.2569967360

-32.4242543286

253438635377865553122983825848491

1.44429258861E-33

32.4038728215

-32.8403448173

579599851728429398674948200821366

5.68045157903E-34

32.7631282657

-33.2456171378

1485360919807422642901860776615607

2.59842885097E-34

33.1718319933

-33.5852891703

3876482907693838530030634129025455

2.11483497389E-34

33.5884378734

-33.6747235161

6267604895580254417159407481435303

1.63124109681E-34

33.7971016111

-33.7874818457

8658726883466670304288180833845151

1.14764721972E-34

33.9374540412

-33.9401915911

11049848871353086191416954186254999

6.64053342637E-35

34.0433563382

-34.1777970329

13440970859239502078545727538664847

1.80459465553E-35

34.1284306395

-34.7436203332

42714034565604922122765955968404389

5.77845195764E-36

34.6305705948

-35.2381884931

157415167403180186412518096334952709

5.06786127522E-36

35.1970465756

-35.2951752818

272116300240755450702270236701501029

4.35727059279E-36

35.4347545576

-35.3607854689

386817433078330714992022377068049349

3.64667991037E-36

35.5875060386

-35.4381023555

501518565915905979281774517434597669

2.93608922794E-36

35.7002870150

-35.5322307503

616219698753481243571526657801145989

2.22549854552E-36

35.7897355773

-35.6525726852

730920831591056507861278798167694309

1.51490786309E-36

35.8638703397

-35.8196137802

845621964428631772151030938534242629

8.04317180668E-37

35.9271762549

-36.0945726544

960323097266207036440783078900790949

9.37264982439E-38

35.9824173744

-37.0281376085

7797285910967231555816016771572875912

3.92213035268E-38

36.8919434592

-37.4064779766

22431534635635487631007267235817836787

2.39374123364E-38

37.3508589865

-37.6209227992

 

2.2.     Table 2: low bound for "a" to exclude the possibility of a general cycle of length N, based on the assumtion of maximal density of set of members

Density of members means, the elements (a1,a2,… an)=(5,7,11,13,…,an) or (a1,a2,… an)=(7,11,13,…,an) or similarly, generally of the form ak+2 = ak+6 and ak+1=ak+2 or ak+1 = ak+4. To make a cycle possible at all, its minimal member a1 must be smaller than the a1 given in the table.

N (cycle length)

smallest excluding a1

 

N (cycle length)

smallest excluding a1

1

5

 

51

83

2

5

 

52

5

3

5

 

53

5

4

5

 

54

17

5

25

 

55

5

6

5

 

56

47

7

5

 

57

5

8

5

 

58

307

9

5

 

59

11

10

23

 

60

5

11

5

 

61

31

12

5

 

62

5

13

5

 

63

125

14

5

 

64

5

15

17

 

65

5

16

5

 

66

23

17

121

 

67

5

18

5

 

68

67

19

5

 

69

5

20

11

 

70

541

21

5

 

71

17

22

53

 

72

5

23

5

 

73

41

24

5

 

74

5

25

11

 

75

185

26

5

 

76

11

27

31

 

77

5

28

5

 

78

25

29

347

 

79

5

30

5

 

80

95

31

5

 

81

5

32

23

 

82

1073

33

5

 

83

17

34

103

 

84

5

35

5

 

85

55

36

5

 

86

5

37

17

 

87

271

38

5

 

88

11

39

53

 

89

5

40

5

 

90

37

41

1133

 

91

5

42

11

 

92

131

43

5

 

93

11

44

31

 

94

3203

45

5

 

95

23

46

181

 

96

5

47

11

 

97

73

48

5

 

98

5

49

23

 

99

401

50

5

 

100

17

 


 

2.3.     Envelope for more coordinates (1600 coordinates up to N=10250)

 

 

2.4.     Envelopes for other problem-configuration: 2S/3N, 2S/5N , 2S/11N

It was interesting,how the envelopes of other configurations would behave. Surprise: they all have the same slope in the trend. That means, the rate-of-approximation is much related.

Plot 3: Envelope-curve for approximation 2S/3N, 2S/5N, 2S/11N

The longer line for k=5 indicates, that this configuration approximates faster to zero

To see the deviation from the trend (with slope –1) I rotate the whole plot by –45° :

Plot 4:Envelope-curves, rotated by 45°

The plot gives the impression as if the curves could be separated using fourier-analysis; but I don't have experience with this.


2.5.     An earlier discussion in sci.math research (may 2004)

I took only the relevant posts, also shortened (or even removed) needless quoting of previous post and formatted text to special style. Use the google-link to look at the original posts.

http://groups.google.de/group/sci.math.research/browse_frm/thread/3fe481e4d991d6da/bdc7f0126c4c3e1a

 

newsgroups: sci.math.research

Betreff: 3^n - 2^n and relatives


Von: Gottfried Helms he...@uni-kassel.de
Datum: Fri, 21 May 2004 13:30:01 +0000 (UTC)

Hi -

I got an unequality, which i'm unable to analytically to disprove.  Does anyone know useful related material?

The inequality, formulating a restriction, arose whily studying the question of a certain, primitive assumed loop in the collatz (3x+1)-problem. Here it goes:

                             3^L  - 1

     powceil2( 3^L ) <= 2^L* -------

                             2^L  - 1

            where    powceil2 ( x) = smallest power 2^S >= x

Empirically the lhs is always *greater* than the rhs (up to L=200)  The benefit of this inequality is, that if it cannot be satisfied, then a primitive loop in the Collatz-problem cannot exist.

One can reformulate this formula for instance to:

                3^L       3^L  - 1

     powceil2( ---- ) <= ----------

                2^L       2^L  - 1

or many other ways... I didn't find a definitve form, where I could directly conclude the impossibility of that inequality.

Someone with an idea?

Regards -           
Gottfried Helms


Von: Gareth McCaughan gareth.mccaug...@pobox.com
Datum: Sun, 23 May 2004 23:00:01 +0000 (UTC)

 

Gottfried Helms <he...@uni-kassel.de> writes:

>  I got an unequality, which i'm unable to analytically to disprove.

>  Does anyone know useful related material?

>  The inequality, formulating a restriction, arose whily studying

>  the question of a certain, primitive assumed loop in the collatz

>  (3x+1)-problem. Here it goes:

>                              3^L  - 1

>      powceil2( 3^L ) <= 2^L* -------

>                              2^L  - 1

>             where    powceil2 ( x) = smallest power 2^S >= x

 

According to theorems mentioned at the start of chapter 3 of Baker's "Transcendental Number Theory", the following is true.

Let A1, ..., An >= 4 and B >= 2, and suppose that ...
    a1,...,an are algebraic numbers with height(ak) <= Ak
    b1,...,bn are rational integers with |bk| <= B.

 

Write

                F := b1 log a1 + ... + bn log an.

Then either

                F=0 or |F| > B^-(C Q log Q),

where

                Q = product(log Ak) and
                C depends only on n and on d, the maximum degree of the ak.

In particular,

                let n=2 and d=1;
                let a1=2, a2=3; and write
                p = b1, q = -b2.

Then this says

                F = |p log 2 - q log 3|
                either F = 0 or |F| > max(p,q)^-C

for a constant C.

C can be found explicitly. Baker's book doesn't give details of how, but they are out there in the literature. There have been advances in this area since Baker's book. (Search Google for "laurent mignotte nesterenko".) The value of C will still be much larger than you'd like :-).

Anyway: if the inequality above (the one you want to prove can't happen) holds then you can find p,q with |F| <= 2^-p or something like that. And if F is small then p and q have to be somewhat similar in size.

Now, if p^-C < F <= 2^-p then -C log p <= -p log 2, so p / log p <= C / log 2. So you can get an upper bound on the size of p. It may or may not be practical then to check all actual values of p up to there.

A nasty back-of-envelope calculation using a version of Laurent-Mignotte-Nestorenko quoted in a paper I've found on the web suggests that actually you get some such bound as

                                |F| >= exp(-17280) / p^(8640+1080 log p)

where those numbers could doubtless be reduced by being less sloppy than I was, but probably not hugely reduced.

So, that would lead to a contradiction when

                               2^-p p^(8640+1080 log p) < exp(-17280)
                               -p + 8640 log p + 1080 (log p)^2 < -17280
                               p - 8640 log p - 1080 (log p)^2 > 17280

which is true provided p >= 298000 or thereabouts.

So ... if I haven't botched the above in any way (which I probably have), you "only" need to check a few hundred thousand values of L. You'd do that in practice by calculating log 3 / log 2 with sufficient accuracy (plain ol' double precision should be fine) and looking to see how close to an integer you can get by multiplying it by an integer up to a few hundred thousand in size.

--

Gareth McCaughan

.sig under construc


Von: Gareth McCaughan gareth.mccaug...@pobox.com
Datum: 25 May 2004 00:30:14 +0100

 

I wrote:

> According to theorems mentioned at the start of chapter 3 of Baker's "Transcendental Number Theory", the following is true.

..

> So ... if I haven't botched the above in any way (which

> I probably have), you "only" need to check a few hundred

> thousand values of L. You'd do that in practice by calculating

> log 3 / log 2 with sufficient accuracy (plain ol' double

> precision should be fine) and looking to see how close to

> an integer you can get by multiplying it by an integer

> up to a few hundred thousand in size.

 

I just received some e-mail from a friend of mine who knows  much more about number theory than I do, observing that  (1) it's rather well known (to those who know such things,  I suppose) that the 3n+1 conjecture itself follows from  some sort of bounds on the approximability of log 3 / log 2  by rationals, and (2) that the required bounds are much  tighter than those obtainable by methods of the sort I  mentioned. So if Gottfried Helms's conjecture is strong  enough to do much for the 3n+1 conjecture (I'm not sure  what a "primitive loop" is, I'm afraid) then the argument  I sketched probably has some big holes in it.

Contrariwise,  if I've somehow managed to break my perfect record of never posting anything to sci.math.research without at  least one serious mistake, then Gottfried's conjecture probably doesn't imply anything very exciting about the Collatz conjecture. It's after midnight local time and I should be in bed, so I shan't attempt to determine which of the three possibilities - the third being that Gottfried and I are both right, and that Gottfried has found a way to make progress on Collatz with weaker inequalities than others have obtained -- is the truth. I'm just sounding a note of caution. :-)

--

Gareth McCaughan

sig under construc


Von: Gottfried Helms he...@uni-kassel.de
Datum: Tue, 25 May 2004 18:17:31 +0200

 

  Gareth McCaughan schrieb::

> I wrote:

>>According to theorems mentioned at the start of chapter 3

>>of Baker's "Transcendental Number Theory", the following is

>>true.

> ..

>>So ... if I haven't botched the above in any way (which

>>I probably have), you "only" need to check a few hundred

>>thousand values of L. You'd do that in practice by calculating

>>log 3 / log 2 with sufficient accuracy (plain ol' double

>>precision should be fine) and looking to see how close to

>>an integer you can get by multiplying it by an integer

>>up to a few hundred thousand in size.

> I just received some e-mail from a friend of mine who knows

> much more about number theory than I do, observing that

> (1) it's rather well known (to those who know such things,

> I suppose) that the 3n+1 conjecture itself follows from

> some sort of bounds on the approximability of log 3 / log 2

> by rationals, and (2) that the required bounds are much

> tighter than those obtainable by methods of the sort I

> mentioned. So if Gottfried Helms's conjecture is strong

> enough to do much for the 3n+1 conjecture (I'm not sure

> what a "primitive loop" is, I'm afraid) then the argument

> I sketched probably has some big holes in it. Contrariwise,

> if I've somehow managed to break my perfect record of

> never posting anything to sci.math.research without at

> least one serious mistake, then Gottfried's conjecture

> probably doesn't imply anything very exciting about the

> Collatz conjecture. It's after midnight local time and

> I should be in bed, so I shan't attempt to determine

> which of the three possibilities -- the third being

> that Gottfried and I are both right, and that Gottfried

> has found a way to make progress on Collatz with weaker

> inequalities than others have obtained -- is the truth.

> I'm just sounding a note of caution. :-)

 

Hmmm, the stated inequality results from a "primitive" loop, let me explain that.

---------------------

 

Assume the transformation T on an odd x with the parameter A

    y= T(x;A)

     being

    y=  (3x+1)/2^A

where A is the highest exponent keeping y integral (which is actually only a short form for multiple steps  of the collatz-transformation, collecting all subsequent x/2 - operations)   and allowing short form for recursive notation:

 

    z= T(y;B)   =  T(T(x;A);B) = T(x;A,B)

  then a loop of, for instance, length 2 occurs, if

    z = T(x;A,B) = x

 

------------------------------------------

The occuring equations are under investigation in some articles, that I've come across (mostly via internet), and are obviously difficult to handle, but of high general interest, as I learned this way.

 

My first approach was to deal with any type of loop, the general form

     x = T(x;A,B,C,D,..M)

       = T(x;A,B,C,D,...,M,A,B,C,...M)

       = T(x;A,B,C...)...

for what I've got some nice results, but still not in the form of a general formulation, which could, for instance, easily been transferred to 5x+1 and other classes of the problem.

So I decided, first to investigate a somehow "primitive" loop.

I assumed most primitive loop (besides the trivial one, which is in this notation  1 = T(1;2) = T(1;2,2) = T(1;2,2,2,2,2,2,...)  ) for my purposes the type of loop, which starts with one or more ascending steps, and then descends in one step. These are the assumed loops of the form

      x = T(x;1,1,1,1,...,1,A)

where immediately strong restrictions apply on A.

 

One reason why I assumed that type as somehow primitive, is, that any eventual loop can be expressed as a collection of ascending steps between descending steps, if the length 0 is allowed.

So an arbitrary transformation, for instance

      y = T(x;1,1,3,1,4,2,1,1,3)

can be segmented in

      y = T( T(T(T(T(x;1,1,3);1,4);2);1,1,3)

and eventually I can use my tools, that I developed in the analysis of the "primitive" loop.

-------------------------------------------------------------

If I analyse the transformation of length N

     z =  T(x;1,1,1,1,...,1,A)   where the number of ones is denoted as "L",

and check, whether it is ever possible, that we find a solution in integers, where z equals x, I come to an expression of the right hand side of my inequality, that I stated her in my previous postings, which also reflects an *additional* restriction.

With an arbitray 3-step-transformation, x' = T(x;A,B,C) with the length N=3, where x' should equal x (thus realizing a loop) with x,y,z, the intermediate values of each transformation, we can formulate a strong restriction on the exponents A,B,C:

    since y = (3x+1)/2^A  ,    z = (3y+1)/2^B   , x'=(3z+1)/2^C  and x=x' assumed (to form a loop), we can write their product as

           (3x+1) (3y+1) (3z+1)
     xyz = ---------------------
             2^(A+B+C)

 

Rearranging this we have:

                 (3x+1) (3y+1) (3z+1)            1          1          1
    2^(A+B+C) = ---------------------   = ( 3 + ---) ( 3 + ---) ( 3 + ---)
                  x   * y *  z                   x          y          z

and obviously the range for the rhs is 3^3 .. 4^3 , so the sum of the exponents S=A+B+C must be an integer, which makes 2^S falling in between this range.

     3^N   <   2^S <=  4^N    (this is valid for any length N of assumed loop)
                              (for generalizations like the 5x+1-problem this
                               is equivalently 5^N < 2^S < 6^N)

 

Even more, this equation shows without any lengthy proof, that whenever the sum S is in general 2*N, then *all* parentheses on the rhs must take their maximum, and this is 4 for each of them.

This restricts then all x,y,z to be 1 , which in turn restricts all A,B,C to be 2.

Result:  if S = 2*N then  x = T(x;A,B,C,D...) only if A=B=C=D=...=2 and x = 1

  ----------------

It also shows a widely unknown property of the loop-problem, that the values of x,y,z have *high bounds* - which is important, since often articles about the collatz-problem assume loops in "high number" areas, if they don't find a solution in small accessible values. That is definitely not true: the values of the members of an eventual loop are much restricted in values.

 

Since the trivial loop is not of interest, we only have to study the cases

                       2^S < 4^N

and since 2^S must be at least the next power of 2 after 3^N we have the inequality

                      powerceil2(3^N) <=    2^S   < 4^N

 

Now from the expansion of the three transformations into explicit formulas  we get possible S; and I observed, that they were *always* smaller than  powerceil2(3^N) in my cases of primitive loops. The contributions here in  sci.math.research , sci.math  and by some private posts showed, that there  is an *extremely* high likelihood, that this inequality never holds.  However - that's still no proof, even not for this simple case.

 

  ----------------------------------------------------------

 

I think, I made the needed progress now by investigating some modular classes, which exhibited a useful, very simple structure for candidate numbers x and y.

The above form of the inequality, stated for a "primitive" loop of length N with L=N-1 ones and one exponent >1

      x = T(x;1,1,1,1,1....1,C)    with L ones, C>1 and x odd integer>1

This problem can be separated into two:

     y = T(x;1,1,1,1,1,1...1)      with L=N-1 ones ("iterated transformation")

     z = T(y;C)                    where z should equal x

An iterated transformation like y=T(x;1,1,1,1,1....1) with L ones restricts x and y to a very specific modular structure. it comes out, that - with a free parameter i ranging of nonnegative odd integers - x and y *must* have a very simple structure depending on the length of the requested iterated transformation:

                                   x = i * 2 * 2^L -1
                                   y = i * 2 * 3^L -1

thus

                          3* ( i * 2 * 3^L -1 ) +1
     z  = (3y+1)/2^C   =  -------------------------
                                2^C

                    and if z = x

                            3* ( i*2*3^L -1 ) +1
     x  = i*2*2^L -1   
=  ----------------------
                                   2^C

 

After rearranging I come to the equation

                          i*3^N -1
              2^C  = 2 * -------------
                          i*2^N -1

and  with S = C + 1*L  the stated inequality must hold:

                                                 i*3^N -1
    powerceil(3^N) <= 2^S = 2^(C+L) = 2^L * 2 * ---------  < 4^N
                                                 i*2^N -1

 

If this inequality does not hold, then such a type of loop cannot exist - irrespectively of any assumend length.

-------------------------------------------------------

I stated this inequality for the case i=1 . For growing i the middle part of the inequality is better written like the following

                           3^N - 1/i
                     2^N * ---------
                           2^N - 1/i

and this converges to 3N, which is definitevely smaller than the lhs:

 

for i->oo the inequality

                                  powerceil2(3^N) <= 3^N

is obviously false.

So the case with i=1 was the most critical case, and I accept the information and learned the arguments for the extremely likelihood, that this inequality cannnot be satisfied for any   parameter L and C but which is still not *proven*....

------------------------------------------------------------------

If that's solved, then at least a "primitive" loop can be actually negated - which is surely no great step in the whole loop-problem or even the general collatz problem - but... it's a start.

Therefore I'm also more interested in extensible proofs than in min/max-estimations for separate cases, if they cannot be generalized to  other collatz-type-problems.

...

Unfortunately, a disproof of this type of collatz-loops is not conversely saying something on the above inequality, insofar it concerns unproved assumtions about the 2-log of 3 and the like, what you and others had derived here - that's bad luck. But I've got the impression, that some of my equations in this context could be helpful for progress even in that regard. I'll post them, if I've time these days.

Hope I answered the questions, that you rose in your post, even if I had difficulties to really follow your four segments today... :-)

Regards -           
Gottfried Helms


Von: Gottfried Helms he...@uni-kassel.de                
Datum: Tue, 25 May 2004 18:26:36 +0200

Gareth McCaughan schrieb::

>       According to theorems mentioned at the start of chapter 3 of Baker's "Transcendental Number Theory", the following is true.
(...)

Hi Gareth -

that's a very interesting material, thank you (hope, I'll ever learn to apply that myself). I'll study it in more detail next days, since I'm guessing another connection to that field here, where my derivations on number-structure possibly could give additional information - or at least some more insight - I'll post it another day.

For an explanation for the origin of my question please see my other post.

Regards -           
Gottfried Helms


Von: stei...@math.bgsu.edu (Ray Steiner)
Datum: 1 Jun 2004 10:48:53 -0700

 

Gottfried Helms <he...@uni-kassel.de> wrote in message <news:c94mv1$jl8$05$1@news.t-online.com>...

>       Am 24.05.04 01:00 schrieb Gareth McCaughan:
>>   Gottfried Helms <he...@uni-kassel.de> writes:

(…)

I proved the nonexistence of a  circuit  in the 3x+1 problem in 1977.

Is this what a "primitive cycle" actually is? A circuit is a cycle with one rise and one fall.

In fact, B. deWeger has recently shown that there is no cycle in the 3x+1 rproblem with less than 69 rises and falls in it. I can actually extend this to 70 and 71 rises and falls with Rhin's inequality which I mentioned in an earlier post.

Regards,             
Ray Steiner


Von: Gottfried Helms he...@uni-kassel.de
Datum: Wed, 02 Jun 2004 17:54:37 +0200

Am 01.06.04 19:48 schrieb Ray Steiner:

>       (…)

Hmm, that's interesting. I called it a "primitive", if there are N-1 steps ascending and 1 step descending, like it is in    (7->11->17)  -> 13 which, written as an transfer only noting the occuring exponents-of-2

                  13 = T(7;1,1,4)

My question was

  "is there any solution in integers x,N,A with
                    x = T(x;1,1,1,1...1,A)   with the 1 (N-1)-times occuring
                                               establishing an N-Step-Loop

  ".

I found this very tight relation to the 3^N - 2^N properties, thus my question here.

The case of only one-raise-one-fall, if that means

                                  x = T(x;1,A)

would then just be a special case of my question and can be proven by enumeration or even modular arithmetic.

But I would like to know, how you accessed the problem of this specific of rises&falls? I have a formula, how you can disprove a circle of *any* finite combination of raises&falls in finite number of tests, let say 100 raises&falls by a number Z of tests, where Z is a combinatorical function of about 42, which I'm bounding down by optimizing my formulas.

My attempt was to generalize these formulas to *unlimited* Z.

The "primitive" Loop is the most simple structure of that general problem of unlimited length, and has very tight and handy relations to the (3/2)^N - structure and that of frac( (3/2)^N), which I'm currently investigating.

---------------------------

Concerning your reference to deWegner:

His literature looks interesting, especially those with the focus on binomials: that was the next idea, that I wanted to step in. As I pointed out in a previor post the related problem can be represented using a rep-unit-form and the question, whether 3^n-1 div 2^N can ever be a repunit base a certain power of 2^P with p reasonably greater than N (don't have it at hand just now). I'm currently studying, what the binomial- expansion of 3^N = (2+1)^N explains for that problem.

Just have seen your reference to Rhin: could you point to a reference?

Regards -           
Gottfried Helms


Von: stei...@math.bgsu.edu (Ray Steiner)
Datum: 1 Jun 2004 10:41:08 -0700

(…)

There is a paper by Georges Rhin(1987) in which he proves that

                |p log 2 - q log 3| >  H^(-13.3),

where

                H = max(p,q)  and
                H > 2.

After that, just check the convergents of log-2(3).

Regards,             
Ray Steiner