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G.f. satisfies A(x) = 1 + x*A(x)*(1 + x^2*A(x)^5).
2

%I #12 Sep 18 2023 09:00:48

%S 1,1,1,2,8,29,91,289,1009,3706,13606,49822,184726,696052,2648746,

%T 10132072,38952970,150635860,585724594,2287631614,8968247626,

%U 35281363830,139256375922,551306272137,2188516471579,8709331962133,34739262293455,138863195368540

%N G.f. satisfies A(x) = 1 + x*A(x)*(1 + x^2*A(x)^5).

%F a(n) = Sum_{k=0..floor(n/3)} binomial(n-2*k,k) * binomial(n+3*k+1,n-2*k) / (n+3*k+1) = Sum_{k=0..floor(n/3)} binomial(n+3*k,6*k) * binomial(6*k,k) / (5*k+1).

%o (PARI) a(n) = sum(k=0, n\3, binomial(n-2*k, k)*binomial(n+3*k+1, n-2*k)/(n+3*k+1));

%Y Cf. A364472, A364523, A365759, A365760.

%Y Cf. A365693.

%K nonn

%O 0,4

%A _Seiichi Manyama_, Sep 18 2023