The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A277684 Least k such that A277109(k) = 2^n - 1. 2
 0, 6, 17, 18, 69, 70, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 464, 465, 466, 467, 624, 625, 1810, 1811, 1812 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Are the terms always increasing? Note, if the conjecture in A277109 is true then the terms in this sequence are guaranteed to be increasing. Since the conjecture in A277109 is true, this sequence is strictly increasing. - Hartmut F. W. Hoft, Aug 16 2018 LINKS EXAMPLE Since A277109(69) = 15 is the first occurrence of 15 = 2^4 - 1, a(4) = 69. - Hartmut F. W. Hoft, Aug 16 2018 MATHEMATICA collatzN[n_] := Length[NestWhileList[If[EvenQ[#], #/2, 3# + 1]&, n, #!=1&]] collatzNrun[n_] := Module[{run=collatzN[n], k=1}, While[collatzN[n+k]==run, k++]; k] power2[k_] := Module[{list=NestWhileList[#/2&, k, EvenQ]}, {Last[list], Length[list]-1}] (* a277684[] computes all values through index n *) a277684[n_] := Module[{i, list={0}}, For[i=1, i<=n, i++, If[power2[collatzNrun[2^i+1]+1] == {1, Length[list]+1}, AppendTo[list, i]]]; list]/; n>0 (* Hartmut F. W. Hoft, Aug 16 2018 *) PROG (PARI) nbsteps(n)= s=n; c=0; while(s>1, s=if(s%2, 3*s+1, s/2); c++); c; len(n) = {my(ns = 2^n+1); my(nbs = nbsteps(ns)); while(nbsteps(ns+1) == nbs, ns++); ns - 2^n; } a(n) = {k=0; while(len(k) != 2^n-1, k++); k; } \\ Michel Marcus, Oct 30 2016 CROSSREFS Cf. A277109. Sequence in context: A063584 A019296 A035484 * A009171 A012417 A184549 Adjacent sequences:  A277681 A277682 A277683 * A277685 A277686 A277687 KEYWORD nonn,more AUTHOR Dmitry Kamenetsky, Oct 26 2016 EXTENSIONS Duplicated term 300 removed by Hartmut F. W. Hoft, Aug 16 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 28 09:20 EDT 2021. Contains 346322 sequences. (Running on oeis4.)