A365132 G.f. satisfies A(x) = (1 + x*A(x)*(1 + x*A(x))^3)^3.
1, 3, 21, 163, 1410, 12954, 124197, 1228269, 12438504, 128338224, 1344328020, 14258394921, 152820980120, 1652596758738, 18008899150278, 197566103218974, 2180167982738235, 24183969704272350, 269513577777159816, 3016075156973165367, 33879382051847177781
Offset: 0
Keywords
Programs
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PARI
a(n, s=3, t=3) = sum(k=0, n, binomial(t*(n+1), k)*binomial(s*k, n-k))/(n+1);
Formula
If g.f. satisfies A(x) = (1 + x*A(x)*(1 + x*A(x))^s)^t, then a(n) = (1/(n+1)) * Sum_{k=0..n} binomial(t*(n+1),k) * binomial(s*k,n-k).