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A363614
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Expansion of Sum_{k>0} x^(2*k)/(1+x^k)^6.
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4
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0, 1, -6, 22, -56, 121, -252, 484, -798, 1232, -2002, 3145, -4368, 5937, -8630, 12112, -15504, 19678, -26334, 34902, -42762, 51129, -65780, 84337, -98336, 114388, -143304, 175869, -201376, 230120, -278256, 336744, -379000, 420394, -502250, 598459, -658008, 723065, -855042, 997962, -1086008
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OFFSET
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1,3
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LINKS
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FORMULA
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G.f.: Sum_{k>0} binomial(k+3,5) * (-x)^k/(1 - x^k).
a(n) = Sum_{d|n} (-1)^d * binomial(d+3,5).
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MATHEMATICA
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a[n_] := DivisorSum[n, (-1)^#*Binomial[# + 3, 5] &]; Array[a, 40] (* Amiram Eldar, Jul 18 2023 *)
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PROG
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(PARI) my(N=50, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(2*k)/(1+x^k)^6)))
(PARI) a(n) = sumdiv(n, d, (-1)^d*binomial(d+3, 5));
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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