The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A125711

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A125711

In the "3x+1" problem, let 1 denote a halving step and 0 denote an x->3x+1 step. Then a(n) is obtained by writing the sequence of steps needed to reach 1 from 2n and reading it as a decimal number.
(history; published version)

#12 by Ray Chandler at Thu Oct 31 11:47:53 EDT 2019

STATUS

editing

approved

#11 by Ray Chandler at Thu Oct 31 11:47:49 EDT 2019

MATHEMATICA

f[x_] := If[EvenQ[x], x/2, 3x + 1]; g[n_] := FromDigits[Mod[Most[NestWhileList[f, 2n, # > 1 &]], 2, 1] - 1, 2]; Table[g[n], {n, 40}] (* Ray Chandler , Feb 02 2007 *)

STATUS

approved

editing

#10 by N. J. A. Sloane at Fri Mar 28 23:41:11 EDT 2014

STATUS

proposed

approved

#9 by Jon E. Schoenfield at Fri Mar 28 23:31:16 EDT 2014

STATUS

editing

proposed

#8 by Jon E. Schoenfield at Fri Mar 28 23:31:14 EDT 2014

MATHEMATICA

f[x_] := If[EvenQ[x], x/2, 3x + 1]; g[n_] := FromDigits[Mod[Most[NestWhileList[f, 2n, # > 1 &]], 2, 1] - 1, 2]; Table[g[n], {n, 40}] (* _Ray Chandler_ *)

STATUS

proposed

editing

#7 by Franklin T. Adams-Watters at Fri Mar 28 18:55:46 EDT 2014

STATUS

editing

proposed

#6 by Franklin T. Adams-Watters at Fri Mar 28 18:55:41 EDT 2014

KEYWORD

nonn,base

STATUS

approved

editing

#5 by Russ Cox at Fri Mar 30 17:29:53 EDT 2012

EXTENSIONS

Extended by _Ray Chandler (rayjchandler(AT)sbcglobal.net), _, Feb 02 2007

Discussion

Fri Mar 30

17:29

OEIS Server: https://oeis.org/edit/global/154

#4 by Russ Cox at Fri Mar 30 16:50:36 EDT 2012

AUTHOR

_N. J. A. Sloane (njas(AT)research.att.com), _, Feb 01 2007

Discussion

Fri Mar 30

16:50

OEIS Server: https://oeis.org/edit/global/110

#3 by N. J. A. Sloane at Fri Feb 27 03:00:00 EST 2009

NAME

In the "3x+1" problem, let 1 denote a halving step and 0 denote an x->3x+1 step. Then a(n) is obtained by writing the sequence of steps needed to reach 1 from 2n, and reading it as a decimal number.

KEYWORD

nonn,new

nonn

AUTHOR

N. J. A. Sloane (njas, (AT)research.att.com), Feb 01 2007