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A007979
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Expansion of (1+x^2)(1+x^4)/((1-x)^2*(1-x^2)*(1-x^3)).
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1
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1, 2, 5, 9, 16, 25, 39, 56, 79, 107, 142, 183, 233, 290, 357, 433, 520, 617, 727, 848, 983, 1131, 1294, 1471, 1665, 1874, 2101, 2345, 2608, 2889, 3191, 3512, 3855, 4219, 4606, 5015, 5449, 5906
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OFFSET
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0,2
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LINKS
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A. R. Calderbank and N. J. A. Sloane, Double circulant codes over Z_4, J. Algeb. Combin., 6 (1997) 119-131 (Abstract, pdf, ps).
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FORMULA
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a(n) = floor((2*n^3+3*n^2+24*n+18)/18). - Tani Akinari, Jun 26 2013
G.f.: (1+x^2)*(1+x^4) / ( (1+x)*(1+x+x^2)*(x-1)^4 ). - R. J. Mathar, Sep 07 2017
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MATHEMATICA
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CoefficientList[Series[(1+x^2)(1+x^4)/((1-x)^2*(1-x^2)*(1-x^3)), {x, 0, 40}], x] (* Vincenzo Librandi, Feb 25 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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