A366184 G.f. A(x) satisfies A(x) = (1 + x*A(x)^3)/(1 - x)^3.
1, 4, 21, 163, 1487, 14697, 153226, 1659338, 18483960, 210437161, 2437721418, 28640748192, 340473075541, 4087735789616, 49494986770104, 603699827411356, 7410709463933414, 91484338902961485, 1135029142529785303, 14145212892466682781, 176993823220824229047
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(n+8*k+2, n-k)*binomial(3*k, k)/(2*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(n+8*k+2,n-k) * binomial(3*k,k)/(2*k+1).