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A176868 Greatest odd number that requires n Collatz (3x+1) iterations to reach 1, or zero if there is no such number. 4
1, 0, 0, 0, 0, 5, 0, 21, 0, 85, 0, 341, 113, 1365, 453, 5461, 1813, 21845, 7281, 87381, 29125, 349525, 116501, 1398101, 466033, 5592405, 1864133, 22369621, 7456533, 89478485, 29826161, 357913941, 119304645, 1431655765, 477218581, 5726623061, 1908874353 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

COMMENTS

Both the 3x+1 steps and the halving steps are counted. a(n)=0 only for n = 1, 2, 3, 4, 6, 8, and 10.

LINKS

T. D. Noe, Table of n, a(n) for n = 0..400

MATHEMATICA

nn = 10; t1 = {0, 0, 5, 21, 85, 341, 1365}; Do[AppendTo[t1, 4 t1[[-1]] + 1], {3*nn}]; t2 = {1, 0, 0, 0, 0, 0, 113}; Do[AppendTo[t2, 4 t2[[-1]] + 1]; AppendTo[t2, 4 t2[[-1]] + 1]; AppendTo[t2, 4 t2[[-1]] + 29], {nn}]; t = Riffle[t2, t1] (* T. D. Noe, Feb 14 2013 *)

CROSSREFS

Cf. A176866, A176867.

Sequence in context: A167355 A282577 A279030 * A279143 A279144 A281741

Adjacent sequences: A176865 A176866 A176867 * A176869 A176870 A176871

KEYWORD

nonn

AUTHOR

T. D. Noe, Apr 27 2010

STATUS

approved

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Last modified November 27 19:48 EST 2022. Contains 358406 sequences. (Running on oeis4.)