%I #8 Nov 11 2023 08:45:05
%S 1,1,6,42,335,2886,26166,246028,2377161,23459250,235452723,2395998060,
%T 24663705924,256358715585,2686893609015,28364934291912,
%U 301334854075058,3219067773992448,34558507062732315,372646872976093760,4034272938342360147
%N G.f. satisfies A(x) = 1 + x*A(x)^3 / (1 - x*A(x)^2)^3.
%F If g.f. satisfies A(x) = 1 + x*A(x)^t / (1 - x*A(x)^u)^s, then a(n) = Sum_{k=0..n} binomial(t*k+u*(n-k)+1,k) * binomial(n+(s-1)*k-1,n-k) / (t*k+u*(n-k)+1).
%o (PARI) a(n, s=3, t=3, u=2) = sum(k=0, n, binomial(t*k+u*(n-k)+1, k)*binomial(n+(s-1)*k-1, n-k)/(t*k+u*(n-k)+1));
%Y Cf. A001764, A367239, A367240.
%K nonn
%O 0,3
%A _Seiichi Manyama_, Nov 11 2023