A380753 E.g.f. A(x) satisfies A(x) = exp(x * A(x)^2) / (1 - x * A(x)^2)^2.
1, 3, 47, 1453, 68349, 4344751, 348936139, 33912469305, 3871084443641, 507765120717691, 75265926888996711, 12443096536067016997, 2270083842550815380725, 453042725968243823206887, 98183026886745981671902979, 22962952582930039784948279281, 5764815614414943166224203759601
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Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n, (2*n+1)^(k-1)*binomial(5*n-k+1, n-k)/k!);
Formula
a(n) = n! * Sum_{k=0..n} (2*n+1)^(k-1) * binomial(5*n-k+1,n-k)/k!.