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A352693
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Expansion of e.g.f. 1 / (1 - Sum_{k>=1} sigma_2(k) * x^k/k!).
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3
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1, 1, 7, 46, 455, 5406, 78172, 1312116, 25214479, 544777183, 13080808752, 345471545728, 9953804592152, 310687941345796, 10443489230611052, 376122782541917166, 14449157656748079247, 589772212576633845886, 25488817336672959449725
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OFFSET
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0,3
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LINKS
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FORMULA
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a(0) = 1; a(n) = Sum_{k=1..n} sigma_2(k) * binomial(n,k) * a(n-k).
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PROG
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(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(1/(1-sum(k=1, N, sigma(k, 2)*x^k/k!))))
(PARI) a(n) = if(n==0, 1, sum(k=1, n, sigma(k, 2)*binomial(n, k)*a(n-k)));
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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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