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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
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| Cf. A121968 a[n]=2*a[n-1]-a[n-2]+n+1.
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FORMULA
| 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
| Table[(9*(n+4)+(n-4)*3^n)/36, {n, 25}]
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CROSSREFS
| Cf. A121968.
Sequence in context: A162273 A092239 A132847 * A018960 A002310 A055728
Adjacent sequences: A121362 A121363 A121364 * A121366 A121367 A121368
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KEYWORD
| nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Sep 06 2006
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