A366239 G.f. A(x) satisfies A(x) = 1 + x + x*(1 + x)^2*A(x)^3.
1, 2, 8, 49, 329, 2401, 18452, 147140, 1206157, 10101011, 86047138, 743288984, 6495476548, 57321239999, 510104531479, 4572492374150, 41247768216331, 374175606700172, 3411195598361653, 31236732721224722, 287182875831208468, 2649838553953071239
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(4*k+1, n-k)*binomial(3*k, k)/(2*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(4*k+1,n-k) * binomial(3*k,k)/(2*k+1).