A377893 E.g.f. A(x) satisfies A(x) = (1 + x*A(x)^3) * exp(x * A(x)^3).
1, 2, 27, 742, 31337, 1796376, 130408603, 11472417104, 1186462228785, 141083381264896, 18966727953873371, 2844742575536036352, 470958524169176911513, 85307709328403287961600, 16782586179544965856158363, 3563492814539574559964993536, 812273035493592514001487147233
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Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n, (3*n+1)^(k-1)*binomial(3*n+1, n-k)/k!);
Formula
a(n) = n! * Sum_{k=0..n} (3*n+1)^(k-1) * binomial(3*n+1,n-k)/k!.