

A222755


Greatest odd number k such that difference between halving and tripling steps in Collatz (3x+1) trajectory of k is n, or 0 if there is no such k.


3



1, 0, 0, 5, 0, 21, 17, 85, 113, 341, 453, 1365, 1813, 5461, 7281, 21845, 29125, 87381, 116501, 349525, 466033, 1398101, 1864133, 5592405, 7456533, 22369621, 29826161, 89478485, 119304645, 357913941, 477218581, 1431655765
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,4


COMMENTS

Note that a(n) <= 2^n, with equality only for n = 0.


LINKS

Table of n, a(n) for n=0..31.


MATHEMATICA

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 15; t = Table[0, {nn}]; Do[c = Collatz[n]; e = Select[c, EvenQ]; diff = 2*Length[e]  Length[c]; If[diff < nn  1, t[[diff + 2]] = n], {n, 1, 2^(nn  1), 2}]; t


CROSSREFS

Cf. A222752, A222753, A222754.
Sequence in context: A283011 A284135 A284177 * A279500 A185246 A279547
Adjacent sequences: A222752 A222753 A222754 * A222756 A222757 A222758


KEYWORD

nonn


AUTHOR

T. D. Noe, Mar 04 2013


EXTENSIONS

a(31) added  T. D. Noe, Mar 05 2013


STATUS

approved



