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Search: id:A138495
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| 0, 1, 1, 1, 3, 9, 15, 25, 55, 121, 231, 441, 903, 1829, 3655, 7225, 14535, 29241, 58311, 116281, 232903
(list; graph; listen)
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OFFSET
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0,5
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FORMULA
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O.g.f.: x/((1-2x)(1+x)(1+2x^2)) . a(n) = a(n-1) +2a(n-3) +4a(n-4). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 19 2008
a(n)= -1/9*(-1)^n+2/9*2^n-1/18*(I*sqrt(2))^n-(1/9*I)*(I*sqrt(2))^n*sqrt(2)+(1/9*I) *sqrt(2)*(-I*sqrt(2))^n-1/18*(-I*sqrt(2))^n, with n>=0 and I=sqrt(-1) - Paolo P. Lava (ppl(AT)spl.at), Jun 03 2008
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CROSSREFS
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Adjacent sequences: A138492 A138493 A138494 this_sequence A138496 A138497 A138498
Sequence in context: A026222 A099989 A085046 this_sequence A055927 A087031 A089632
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KEYWORD
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nonn
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AUTHOR
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Paul Curtz (bpcrtz(AT)free.fr), May 18 2008
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