A127887 Indices of nonzero terms of A127886.

9, 18, 27, 28, 31, 33, 36, 37, 39, 41, 43, 47, 49, 50, 54, 55, 56, 57, 59, 62, 63, 65, 66, 71, 72, 73, 74, 78, 79, 82, 83, 86, 87, 89, 91, 94, 95, 97, 98, 99, 100, 103, 105, 107, 108, 109, 110, 111, 112, 114, 115, 118, 119, 121, 123, 124, 125, 126, 129, 130, 131, 132, 133, 134, 135, 137, 139, 142, 143, 144, 145

Offset

1,1

Comments

These are the numbers for which allowing the choice of x/2 or 3x+1 in the "3x+1" iteration makes a difference in the minimal number of steps to reach 1.

Thus these are the n for which A006577(n) > A127885(n).

Links

Antti Karttunen, Table of n, a(n) for n = 1..695 (computed from the b-files of A006577 and A127885)

Mathematica

Position[#, k_ /; k > 0][[All, 1]] &@ Table[Length@ NestWhileList[If[OddQ@ #, 3 # + 1, #/2] &, n, # > 1 &] - Length@ NestWhileList[Flatten[# /. {k_ /; OddQ@ k :> 3 k + 1, k_ /; EvenQ@ k :> {k/2, 3 k + 1}}] &, {n}, FreeQ[#, 1] &], {n, 126}] (* Michael De Vlieger, Aug 20 2017 *)

Crossrefs

Cf. A006577, A127885, A127886.

Sequence in context: A121282 A205716 A110529 * A359225 A037337 A119310

Adjacent sequences: A127884 A127885 A127886 * A127888 A127889 A127890

Keyword

nonn

Author

David Applegate and N. J. A. Sloane, Feb 04 2007

Extensions

More terms from Antti Karttunen, Aug 18 2017

Status

approved