A377891 E.g.f. A(x) satisfies A(x) = (1 + x*A(x)^3) * exp(x * A(x)).
1, 2, 19, 364, 10665, 423056, 21221851, 1288931456, 91977076561, 7543664425216, 699290913249891, 72306463481715200, 8251192866018497401, 1030074741274860240896, 139650729116792108398891, 20432888021354725476499456, 3209204194084043665909835937, 538542735919965101952197525504
Offset: 0
Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n, (3*n-2*k+1)^(k-1)*binomial(3*n-2*k+1, n-k)/k!);
Formula
a(n) = n! * Sum_{k=0..n} (3*n-2*k+1)^(k-1) * binomial(3*n-2*k+1,n-k)/k!.