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A001305
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Expansion of 1/((1-x)^2*(1-x^2)*(1-x^5)*(1-x^10)*(1-x^20)).
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1
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1, 2, 4, 6, 9, 13, 18, 24, 31, 39, 50, 62, 77, 93, 112, 134, 159, 187, 218, 252, 293, 337, 388, 442, 503, 571, 646, 728, 817, 913, 1022, 1138, 1267, 1403, 1552, 1714, 1889, 2077, 2278, 2492, 2728, 2977, 3248, 3532, 3838, 4166, 4516, 4888, 5282, 5698, 6148
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OFFSET
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0,2
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (2, 0, -2, 1, 1, -2, 0, 2, -1, 1, -2, 0, 2, -1, -1, 2, 0, -2, 1, 1, -2, 0, 2, -1, -1, 2, 0, -2, 1, -1, 2, 0, -2, 1, 1, -2, 0, 2, -1).
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FORMULA
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G.f.: 1/((1-x)^2*(1-x^2)*(1-x^5)*(1-x^10)*(1-x^20)).
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MATHEMATICA
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CoefficientList[Series[1/((1-x)^2*(1-x^2)*(1-x^5)*(1-x^10)*(1-x^20)), {x, 0, 50}], x] (* Vincenzo Librandi, Feb 24 2012 *)
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PROG
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(Maxima) a(n):=block([f:divide((1-z^20)^5, (1-z)^2*(1-z^2)*(1-z^5)*(1-z^10), z)[1]], return(sum(binomial(k+5, 5)*coeff(f, z, n-20*k), k, max(0, ceiling((n-81)/20)), floor(n/20)))); /* Tani Akinari, May 12 2014 */
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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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