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Search: id:A121365
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| A121365 |
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a(n)=6*a(n-1)-9*a(n-2)+n+1. |
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+0
1
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| 1, 1, 1, 2, 9, 43, 185, 732, 2737, 9845, 34449, 118102, 398585, 1328607, 4384393, 14348912, 46633953, 150663529, 484275617, 1549681962, 4939611241, 15690529811, 49686677721, 156905298052, 494251688849
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OFFSET
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1,4
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COMMENT
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Cf. A121968 a[n]=2*a[n-1]-a[n-2]+n+1.
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FORMULA
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a(n)=(36 + (n-4)*3^n + 9*n)/36, n=1,2,...
O.g.f.: -x*(-1+7*x-15*x^2+8*x^3)/((-1+x)^2*(3*x-1)^2). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 10 2007
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MATHEMATICA
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Table[(9*(n+4)+(n-4)*3^n)/36, {n, 25}]
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CROSSREFS
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Cf. A121968.
Adjacent sequences: A121362 A121363 A121364 this_sequence A121366 A121367 A121368
Sequence in context: A056845 A092239 A132847 this_sequence A018960 A002310 A055728
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Sep 06 2006
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