A366222 G.f. A(x) satisfies A(x) = 1 + x*(1 + x)^4*A(x)^3.
1, 1, 7, 42, 287, 2114, 16338, 130802, 1075355, 9025656, 77021482, 666267502, 5829209046, 51492030953, 458612500526, 4113879873624, 37133888342707, 337041718357465, 3074153880004188, 28162578841220534, 259020296989987934, 2390818256963083305
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(4*k, n-k)*binomial(3*k, k)/(2*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(4*k,n-k) * binomial(3*k,k)/(2*k+1).