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A127887 Indices of nonzero terms of A127886. 3
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 (list; graph; refs; listen; history; text; internal format)
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 * A037337 A119310 A037993

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

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Last modified January 18 15:25 EST 2021. Contains 340254 sequences. (Running on oeis4.)