A377632 E.g.f. satisfies A(x) = 1/(1 - x * A(x)^2 * exp(x*A(x)^2))^2.
1, 2, 26, 666, 26000, 1372650, 91594812, 7398109838, 701939170256, 76538939053842, 9432015136260500, 1296420805666136502, 196648127058577395192, 32631136680788714502746, 5880120898119055583177756, 1143520026572037679360951710, 238712613798193658499743637152
Offset: 0
Keywords
Programs
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PARI
a(n) = 2*n!*sum(k=0, n, k^(n-k)*binomial(4*n+k+2, k)/((4*n+k+2)*(n-k)!));
Formula
E.g.f.: B(x)^2, where B(x) is the e.g.f. of A377631.
a(n) = 2 * n! * Sum_{k=0..n} k^(n-k) * binomial(4*n+k+2,k)/( (4*n+k+2)*(n-k)! ).