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A011851
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a(n) = floor(binomial(n,5)/5).
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3
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0, 0, 0, 0, 0, 0, 1, 4, 11, 25, 50, 92, 158, 257, 400, 600, 873, 1237, 1713, 2325, 3100, 4069, 5266, 6729, 8500, 10626, 13156, 16146, 19656, 23751, 28501, 33982, 40275, 47467, 55651, 64926, 75398, 87179, 100388, 115151, 131601, 149879, 170133, 192519, 217201, 244351, 274150
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OFFSET
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0,8
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (6, -15, 20, -15, 5, 5, -15, 20, -15, 5, 5, -15, 20, -15, 5, 5, -15, 20, -15, 5, 5, -15, 20, -15, 6, -1).
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FORMULA
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G.f.: x^6*(x^19 -4*x^18 +8*x^17 -8*x^16 +4*x^15 -3*x^13 +6*x^12 -6*x^11 +3*x^10 -2*x^8 +4*x^7 -4*x^6 +2*x^5 -x^3 +2*x^2 -2*x +1) / ((x -1)^6*(x^20 +x^15 +x^10 +x^5 +1)). [Colin Barker, Jan 23 2013]
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MAPLE
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MATHEMATICA
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CoefficientList[Series[x^6 (x^19 - 4 x^18 + 8 x^17 - 8 x^16 + 4 x^15 - 3 x^13 + 6 x^12 - 6 x^11 + 3 x^10 - 2 x^8 + 4 x^7 - 4 x^6 + 2 x^5 - x^3 + 2 x^2 - 2 x + 1)/((x - 1)^6 (x^20 + x^15 + x^10 + x^5 + 1)), {x, 0, 50}], x] (* Vincenzo Librandi, Oct 15 2013 *)
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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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