

A028352


A Golomblike recurrence that decreases infinitely often.


1



2, 8, 6, 4, 2, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, 72, 70, 68, 66, 64, 62, 60, 58, 56, 54, 52, 50, 48, 46, 44, 42, 40, 38, 36, 34, 32, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, 216, 214, 212, 210, 208, 206, 204, 202
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OFFSET

1,1


COMMENTS

The sequence is a solution to the recursion a(a(n) + n) = a(n) + 4n, which is similar to the Golomb recursion b(b(n) + kn) = 2b(n) + kn, k=1,2,...


LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000
E. J. Barbeau, J. Chew and S. Tanny, A matrix dynamics approach to Golomb's recursion, Electronic J. Combinatorics, #4.1 16 1997.


FORMULA

a(1)=1, a(2*3^m+r) = 8*3^m  2r with m=0, 1, 2, ..., 0 <= r <= 4*3^m  1.  Ralf Stephan, Jan 16 2003
a(n) = 12*3^floor(log(n/2)/log(3))  2*n.  Benoit Cloitre, Jan 23 2003


MATHEMATICA

Table[12*3^Floor[Log[n/2]/Log[3]]  2*n , {n, 1, 50}] (* G. C. Greubel, Nov 27 2016 *)


PROG

(PARI) a(n) = if(n==1, 2, m=floor(log(n/2)/log(3)); r=n2*3^m; 8*3^m2*r)


CROSSREFS

Sequence in context: A175803 A019986 A146943 * A132699 A248413 A206099
Adjacent sequences: A028349 A028350 A028351 * A028353 A028354 A028355


KEYWORD

nonn,easy


AUTHOR

Simon Plouffe


EXTENSIONS

Edited by Ralf Stephan, Jan 16 2003


STATUS

approved



