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A162256
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a(n) = (2*n^3 + 5*n^2 - 3*n)/2.
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2
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2, 15, 45, 98, 180, 297, 455, 660, 918, 1235, 1617, 2070, 2600, 3213, 3915, 4712, 5610, 6615, 7733, 8970, 10332, 11825, 13455, 15228, 17150, 19227, 21465, 23870, 26448, 29205, 32147, 35280, 38610, 42143, 45885, 49842, 54020, 58425, 63063, 67940
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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G.f.: x*(2 + 7*x - 3*x^2)/(1-x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). (End)
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MATHEMATICA
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LinearRecurrence[{4, -6, 4, -1}, {2, 15, 45, 98}, 50] (* or *) CoefficientList[Series[(2+7*x-3*x^2)/(1-x)^4, {x, 0, 39}], x] (* Vincenzo Librandi, Mar 04 2012 *)
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PROG
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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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