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A083658 a(n) = a(n-1) + a(n-2) + gcd(a(n-1),a(n-2)) for n>1, with a(0)=1, a(1)=1. 4
1, 1, 3, 5, 9, 15, 27, 45, 81, 135, 243, 405, 729, 1215, 2187, 3645, 6561, 10935, 19683, 32805, 59049, 98415, 177147, 295245, 531441, 885735, 1594323, 2657205, 4782969, 7971615, 14348907, 23914845, 43046721, 71744535, 129140163, 215233605, 387420489 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..36.

Index entries for linear recurrences with constant coefficients, signature (0,3)

FORMULA

a(2n) = 3^n, a(2n+1) = 5*3^(n-1) for n>0, with a(0)=1, a(1)=1.

G.f.: (2*x^3+1+x)/(1-3*x^2). [R. J. Mathar, Feb 27 2010]

MATHEMATICA

CoefficientList[Series[(-2*x^3 - x - 1)/(3*x^2 - 1), {x, 0, 200}], x] (* Vladimir Joseph Stephan Orlovsky, Jun 10 2011 *)

CROSSREFS

Sequence in context: A147087 A140190 A298352 * A018436 A018298 A017913

Adjacent sequences:  A083655 A083656 A083657 * A083659 A083660 A083661

KEYWORD

nonn,easy

AUTHOR

Paul D. Hanna, Jun 13 2003

STATUS

approved

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Last modified August 24 02:32 EDT 2019. Contains 326260 sequences. (Running on oeis4.)