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A083658
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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.
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2
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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; internal format)
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OFFSET
| 0,3
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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). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 27 2010]
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MATHEMATICA
| CoefficientList[Series[(-2*x^3 - x - 1)/(3*x^2 - 1), {x, 0, 200}], x] (* From Vladimir Joseph Stephan Orlovsky, June 10 2011 *)
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CROSSREFS
| Sequence in context: A029485 A147087 A140190 * A018436 A018298 A017913
Adjacent sequences: A083655 A083656 A083657 * A083659 A083660 A083661
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KEYWORD
| nonn
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AUTHOR
| Paul D. Hanna (pauldhanna(AT)juno.com), Jun 13 2003
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