A381943 G.f. A(x) satisfies A(x) = B(x*A(x)) / (1 - x)^2, where B(x) is the g.f. of A001764.
1, 3, 11, 60, 425, 3426, 29619, 267738, 2497889, 23866056, 232325475, 2295889266, 22971682893, 232248775669, 2368969672183, 24348849065860, 251930963865061, 2621914660411919, 27428338267887815, 288258167672381602, 3042002859317810001, 32222429872821051817
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(4*k+1, k)*binomial(n+k+1, n-k)/(4*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(4*k+1,k) * binomial(n+k+1,n-k)/(4*k+1).