A375267 Number of iterations of the A375265 map to reach 1 starting from n, or -1 if 1 is never reached.

0, 1, 1, 2, 5, 2, 16, 3, 2, 6, 14, 3, 9, 17, 6, 4, 12, 3, 20, 7, 17, 15, 15, 4, 23, 10, 3, 18, 18, 7, 106, 5, 15, 13, 13, 4, 21, 21, 10, 8, 109, 18, 29, 16, 7, 16, 104, 5, 24, 24, 13, 11, 11, 4, 112, 19, 21, 19, 32, 8, 19, 107, 18, 6, 27, 16, 27, 14, 16, 14, 102

Offset

1,4

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Index entries for sequences related to 3x+1 (or Collatz) problem.

Example

a(10) = 6 because the trajectory 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1 consists of 6 steps.

Mathematica

A375265[n_] := Which[Divisible[n, 3], n/3, Divisible[n, 2], n/2, True, 3*n + 1];
Array[Length[NestWhileList[A375265, #, # > 1 &]] - 1 &, 100]

Crossrefs

(Row lengths of A375266) - 1.

Cf. A006577, A006666, A375280.

Sequence in context: A098886 A286785 A340043 * A257514 A089120 A286452

Adjacent sequences: A375264 A375265 A375266 * A375268 A375269 A375270

Keyword

nonn,easy

Author

Paolo Xausa, Aug 09 2024

Status

approved