

A102421


To get a(n), start with 2n+1, multiply by 3 and add 1 and divide out any power of 2; then multiply by 3 and subtract 1 and divide out any power of 2.


4



1, 7, 1, 1, 5, 25, 7, 17, 19, 43, 1, 13, 7, 61, 1, 35, 37, 79, 5, 11, 23, 97, 25, 53, 55, 115, 7, 31, 1, 133, 17, 71, 73, 151, 19, 5, 41, 169, 43, 89, 91, 187, 1, 49, 25, 205, 13, 107, 109, 223, 7, 29, 59, 241, 61, 125, 127, 259, 1, 67, 17, 277, 35, 143, 145, 295, 37, 19, 77, 313
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OFFSET

0,2


COMMENTS

"Start with 2n+1, multiply by 3 and add 1 and divide out any power of 2;" is "equivalent to Start with 3n+2, divide out any power of 2;"  David A. Corneth, Aug 22 2020


LINKS

David A. Corneth, Table of n, a(n) for n = 0..9999


FORMULA

a(n) = A337349(2*n+1).  R. J. Mathar, Aug 24 2020


EXAMPLE

n=1, 2n+1 = 3 > 10 > 5; 5 > 14 >7 = a(1).
n=17, 2*n+1 = 35 > 106 >53; 53 > 158 > 79 = a(17).


MAPLE

A102421 :=proc(n) local j; j:=3*n+1; while j mod 2 = 0 do j:=j/2; od: j:=3*j1; while j mod 2 = 0 do j:=j/2; od: j; end proc;


MATHEMATICA

nextx[x_Integer] := Block[{ a = x}, a = 3a + 1; While[EvenQ@a, a /= 2]; a = 3a  1; While[EvenQ@a, a /= 2]; a]; Table[ nextx[2n + 1], {n, 0, 69}] (* Robert G. Wilson v Sep 20 2006 *)


PROG

(PARI) a(n) = {n = 3*n + 2; n>>=valuation(n, 2); n = 3*n  1; n >> valuation(n, 2)} \\ David A. Corneth, Aug 22 2020


CROSSREFS

Cf. A000265, A102423.
Sequence in context: A019980 A258986 A086384 * A019620 A105395 A120437
Adjacent sequences: A102418 A102419 A102420 * A102422 A102423 A102424


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, based on email from Dan Asimov (dasimov(AT)earthlink.net), Sep 15 2006


EXTENSIONS

Moved comments to A337349.  R. J. Mathar, Aug 24 2020


STATUS

approved



