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8, 27, 63, 122, 210, 333, 497, 708, 972, 1295, 1683, 2142, 2678, 3297, 4005, 4808, 5712, 6723, 7847, 9090, 10458, 11957, 13593, 15372, 17300, 19383, 21627, 24038, 26622, 29385, 32333, 35472, 38808, 42347, 46095, 50058, 54242, 58653, 63297
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n)=n*(2*n^2+5*n+9)/2 = 4*a(n-1)-6*a(n-2)+4*a(n-3)-a(n-4). G.f.: x*(8-5*x+3*x^2)/(x-1)^4. [From R. J. Mathar, May 31 2009]
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MATHEMATICA
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CoefficientList[Series[(8-5*x+3*x^2)/(x-1)^4, {x, 0, 40}], x] (* Vincenzo Librandi, Jun 30 2012 *)
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PROG
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(Magma) I:=[8, 27, 63, 122]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..50]]; // Vincenzo Librandi, Jun 30 2012
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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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EXTENSIONS
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STATUS
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approved
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