A371893 G.f. A(x) satisfies A(x) = 1 + x/A(x)^2 * (1 + A(x)^4).
1, 2, 0, 16, -32, 336, -1472, 10944, -63744, 441088, -2866688, 19772416, -134832128, 941381632, -6585720832, 46607831040, -331406262272, 2373110628352, -17072541007872, 123438375763968, -896088779128832, 6530356893777920, -47752086733717504
Offset: 0
Keywords
Programs
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PARI
a(n) = if(n==0, 1, (-1)^(n-1)*sum(k=0, n, binomial(n, k)*binomial(3*n-4*k-2, n-1))/n);
Formula
a(n) = (-1)^(n-1) * (1/n) * Sum_{k=0..n} binomial(n,k) * binomial(3*n-4*k-2,n-1) for n > 0.