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A102423
Start at x=2n+1, iterate the map x -> A337349(x); sequence gives smallest number in the resulting cycle, or -1 if the trajectory never cycles.
4
1, 1, 1, 1, 1, 1, 1, 17, 17, 17, 1, 1, 1, 17, 1, 1, 1, 1, 1, 1, 1, 17, 1, 1, 1, 1, 1, 1, 1, 1, 17, 1, 1, 1, 17, 1, 1, 17, 17, 1, 1, 1, 1, 1, 1, 1, 1, 17, 17, 1, 1, 1, 1, 17, 17, 1, 1, 1, 1, 1, 17, 17, 1, 1, 1, 1, 1, 17, 17, 1, 1, 1, 1, 1, 1, 1, 17, 1, 1, 1, 1, 1, 1, 1, 17, 17, 17, 1, 1, 1, 1, 1, 1, 1, 1
OFFSET
0,8
COMMENTS
See A102421 and A337349 for further comments.
LINKS
MATHEMATICA
nextx[x_Integer] := Block[{a = x}, a = 3a + 1; While[EvenQ@a, a /= 2]; a = 3a - 1; While[EvenQ@a, a /= 2]; a]; f[n_] := NestWhile[nextx, n, FreeQ[{1, 17, 19, 43, 97, 109, 61}, # ] &]; Table[ If[ f[2n + 1] == 1, 1, 17], {n, 0, 94}] (* Robert G. Wilson v, Sep 20 2006; added 61 to comparison set used for detecting cycles, William P. Orrick, Aug 24 2020; should be "!" prefixing MemberQ, changed to FreeQ, Ray Chandler, Aug 28 2020 *)
CROSSREFS
Cf. A102421, A122563 (iterations to enter cycle), A337349.
Sequence in context: A371997 A291370 A291432 * A010856 A291515 A216436
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, based on email from Dan Asimov (dasimov(AT)earthlink.net), Sep 15 2006
EXTENSIONS
More terms from Robert G. Wilson v, Sep 20 2006
Replaced A102421 by A337349 in NAME. - R. J. Mathar, Aug 24 2020
STATUS
approved