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A355508
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E.g.f. satisfies log(A(x)) = x^2 * (exp(x * A(x)) - 1) * A(x).
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1
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1, 0, 0, 6, 12, 20, 1830, 15162, 82376, 3326472, 59467050, 678585710, 20553790092, 563969783676, 10776243950654, 318310813941330, 10988438698692240, 303144002003606672, 9910024990673571666, 392381835437286982998, 14072003919511407720020
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) = n! * Sum_{k=0..floor(n/3)} (n-k+1)^(k-1) * Stirling2(n-2*k,k)/(n-2*k)!.
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MATHEMATICA
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m = 21; (* number of terms *)
A[_] = 0;
Do[A[x_] = Exp[x^2*(Exp[x*A[x]] - 1)*A[x]] + O[x]^m // Normal, {m}];
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PROG
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(PARI) a(n) = n!*sum(k=0, n\3, (n-k+1)^(k-1)*stirling(n-2*k, k, 2)/(n-2*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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