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A004657
Expansion of g.f.: (1+x^3)*(1+x^4)/((1-x)*(1-x^2)^2*(1-x^4)).
2
1, 1, 3, 4, 9, 11, 19, 24, 37, 45, 63, 76, 101, 119, 151, 176, 217, 249, 299, 340, 401, 451, 523, 584, 669, 741, 839, 924, 1037, 1135, 1263, 1376, 1521, 1649, 1811, 1956, 2137, 2299, 2499, 2680, 2901, 3101
OFFSET
0,3
REFERENCES
M. Klemm, Selbstduale Codes ueber dem Ring der ganzen Zahlen modulo 4, Arch. Math. (Basel), 53 (1989), 201-207.
LINKS
G. Nebe, E. M. Rains and N. J. A. Sloane, Self-Dual Codes and Invariant Theory, Springer, Berlin, 2006.
A. R. Calderbank and N. J. A. Sloane, Double circulant codes over Z_4, J. Algeb. Combin., 6 (1997) 119-131 (Abstract, pdf, ps).
FORMULA
G.f.: (x^2-x+1)*(1+x^4) / ( (x^2+1)*(1+x)^2*(x-1)^4 ). - R. J. Mathar, Dec 18 2014
MATHEMATICA
CoefficientList[Series[(x^2 - x + 1)*(1 + x^4)/((x^2 + 1)*(1 + x)^2*(x - 1)^4), {x, 0, 50}], x] (* G. C. Greubel, Sep 10 2018 *)
PROG
(PARI) x='x+O('x^50); Vec((x^2-x+1)*(1+x^4)/((x^2+1)*(1+x)^2*(x-1)^4)) \\ G. C. Greubel, Sep 10 2018
(Magma) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((x^2-x+1)*(1+x^4)/((x^2+1)*(1+x)^2*(x-1)^4))); // G. C. Greubel, Sep 10 2018
CROSSREFS
Sequence in context: A176744 A023420 A376654 * A054075 A366753 A062798
KEYWORD
nonn
EXTENSIONS
Definition corrected by N. J. A. Sloane, Apr 08 2004
STATUS
approved