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A002999
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Expansion of (1 + x*exp(x))^2.
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3
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1, 2, 6, 18, 56, 170, 492, 1358, 3600, 9234, 23060, 56342, 135192, 319514, 745500, 1720350, 3932192, 8912930, 20054052, 44826662, 99614760, 220201002, 484442156, 1061158958, 2315255856, 5033164850, 10905190452, 23555211318, 50734301240, 108984795194
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OFFSET
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0,2
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LINKS
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FORMULA
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a(0) = 1, a(n) = (n^2 - n)*2^n/4 + 2*n.
G.f.: 1+(2x(7x^3-10x^2+5x-1))/((x-1)^2 (2x-1)^3). - Harvey P. Dale, Apr 04 2011
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MATHEMATICA
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CoefficientList[Series[1+(2x(7x^3-10x^2+5x-1))/((x-1)^2 (2x-1)^3), {x, 0, 30}], x] (* Harvey P. Dale, Apr 04 2011 *)
Table[If[n == 0, 1, (n^2 - n) 2^n/4 + 2*n], {n, 0, 30}] (* T. D. Noe, Apr 04 2011 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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