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A011925
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a(n) = floor(n*(n-1)*(n-2)*(n-3)/15).
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1
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0, 0, 0, 0, 1, 8, 24, 56, 112, 201, 336, 528, 792, 1144, 1601, 2184, 2912, 3808, 4896, 6201, 7752, 9576, 11704, 14168, 17001, 20240, 23920, 28080, 32760, 38001, 43848, 50344, 57536, 65472, 74201, 83776
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OFFSET
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0,6
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LINKS
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FORMULA
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a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) + a(n-5) - 4*a(n-6) + 6*a(n-7) - 4*a(n-8) + a(n-9).
G.f.: x^4*(x^4 + 4*x^3 - 2*x^2 + 4*x + 1) / ( (1-x)^5*(x^4 + x^3 + x^2 + x + 1) ). (End)
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MAPLE
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MATHEMATICA
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CoefficientList[Series[x^4*(x^4+4*x^3-2*x^2+4*x+1)/((1-x)^5*(x^4+x^3+x^2+x+1)), {x, 0, 50}], x] (* Vincenzo Librandi, Jun 19 2012 *)
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PROG
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(Magma) [Floor(n*(n-1)*(n-2)*(n-3)/15): n in [0..45]]; // Vincenzo Librandi, Jun 19 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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STATUS
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approved
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