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A307067
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Expansion of 1/(2 - Product_{k>=2} (1 + x^k)).
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2
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1, 0, 1, 1, 2, 4, 6, 12, 19, 36, 60, 108, 187, 328, 576, 1005, 1765, 3084, 5408, 9461, 16575, 29017, 50812, 88977, 155792, 272813, 477684, 836466, 1464654, 2564685, 4490833, 7863610, 13769463, 24110774, 42218847, 73926591, 129448088, 226667986, 396903536, 694991728
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OFFSET
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0,5
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COMMENTS
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LINKS
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FORMULA
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a(0) = 1; a(n) = Sum_{k=1..n} A025147(k)*a(n-k).
G.f.: (1+x)/(2*(1+x) - QP(x^2)/QP(x)), where QP(x) = QPochhammer(x).
G.f.: (1+x)/(2*(1+x) - x^(1/24)*eta(x^2)/eta(x)), where eta(x) is the Dedekind eta function. (End)
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MAPLE
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a:=series(1/(2-mul((1+x^k), k=2..100)), x=0, 40): seq(coeff(a, x, n), n=0..39); # Paolo P. Lava, Apr 03 2019
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MATHEMATICA
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nmax = 39; CoefficientList[Series[1/(2 - Product[(1 + x^k), {k, 2, nmax}]), {x, 0, nmax}], x]
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PROG
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(Magma)
m:=80;
R<x>:=PowerSeriesRing(Integers(), m);
Coefficients(R!( 1/(2 - (&*[1+x^j: j in [2..m+2]])) )); // G. C. Greubel, Jan 24 2024
(SageMath)
m=80;
def f(x): return 1/( 2 - product(1+x^j for j in range(2, m+3)) )
P.<x> = PowerSeriesRing(QQ, prec)
return P( f(x) ).list()
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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