A222755 - OEIS

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.

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

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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