A176868 Greatest odd number that requires n Collatz (3x+1) iterations to reach 1, or zero if there is no such number.

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

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