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A328994
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a(n) = n^2*(1+n)*(1+n^2)/4.
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1
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1, 15, 90, 340, 975, 2331, 4900, 9360, 16605, 27775, 44286, 67860, 100555, 144795, 203400, 279616, 377145, 500175, 653410, 842100, 1072071, 1349755, 1682220, 2077200, 2543125, 3089151, 3725190, 4461940, 5310915, 6284475, 7395856, 8659200, 10089585
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6).
G.f.: x*(1+9*x+15*x^2+5*x^3)/(1-x)^6. (End)
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MATHEMATICA
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CoefficientList[Series[(1+9x+15x^2+5x^3)/(1-x)^6, {x, 0, 33}], x] (* Vincenzo Librandi, Nov 13 2019 *)
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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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