A380755 E.g.f. A(x) satisfies A(x) = exp(x * A(x)^2 / (1 - x * A(x)^2)^2) / (1 - x * A(x)^2).
1, 2, 25, 622, 23601, 1211306, 78585241, 6171434550, 569338685089, 60362321078674, 7232765564919321, 966640735654507838, 142570635491126076625, 23003561321179411452858, 4030628821337323603113241, 762175215630679850520288646, 154707566043362563540600474689
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Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n, (2*n+1)^(k-1)*binomial(3*n+k, n-k)/k!);
Formula
a(n) = n! * Sum_{k=0..n} (2*n+1)^(k-1) * binomial(3*n+k,n-k)/k!.