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A008809
Expansion of (1+x^9)/((1-x^2)^2*(1-x^9)).
1
1, 0, 2, 0, 3, 0, 4, 0, 5, 2, 6, 4, 7, 6, 8, 8, 9, 10, 12, 12, 15, 14, 18, 16, 21, 18, 24, 22, 27, 26, 30, 30, 33, 34, 36, 38, 41, 42, 46, 46, 51, 50, 56, 54, 61, 60, 66, 66, 71, 72, 76, 78, 81, 84, 88, 90, 95, 96, 102, 102, 109, 108, 116, 116, 123, 124, 130
OFFSET
0,3
LINKS
FORMULA
G.f.: (1+x^9)/((1-x^2)^2*(1-x^9)). - G. C. Greubel, Sep 12 2019
G.f.: (1-x^3+x^6)*(1-x+x^2)/((1-x)^3*(1+x+x^2)*(1+x)*(1+x^3+x^6)). - R. J. Mathar, Feb 04 2022
MAPLE
seq(coeff(series((1+x^9)/((1-x^2)^2*(1-x^9)), x, n+1), x, n), n = 0..70); # G. C. Greubel, Sep 12 2019
MATHEMATICA
CoefficientList[Series[(1+x^9)/((1-x^2)^2*(1-x^9)), {x, 0, 70}], x] (* G. C. Greubel, Sep 12 2019 *)
PROG
(PARI) my(x='x+O('x^70)); Vec((1+x^9)/((1-x^2)^2*(1-x^9))) \\ G. C. Greubel, Sep 12 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 70); Coefficients(R!( (1+x^9)/((1-x^2)^2*(1-x^9)) )); // G. C. Greubel, Sep 12 2019
(Sage)
def A008809_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P((1+x^9)/((1-x^2)^2*(1-x^9))).list()
A008809_list(70) # G. C. Greubel, Sep 12 2019
(GAP) a:=[1, 0, 2, 0, 3, 0, 4, 0, 5, 2, 6, 4];; for n in [13..70] do a[n]:=a[n-1] +a[n-2]-a[n-3]+a[n-9]-a[n-10]-a[n-11]+a[n-12]; od; a; # G. C. Greubel, Sep 12 2019
CROSSREFS
Sequence in context: A263396 A029180 A008802 * A008821 A194749 A284969
KEYWORD
nonn,easy
STATUS
approved