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G.f. satisfies A(x) = 1 + x*A(x) - x^2*A(x)^4.
2

%I #8 Nov 02 2023 10:40:27

%S 1,1,0,-4,-10,2,89,249,-91,-2811,-8071,4201,103617,297201,-200421,

%T -4167581,-11798389,9803475,177275251,492087227,-488311177,

%U -7839760737,-21249466773,24651743523,356735365223,941396264159,-1257287146286,-16589782316762

%N G.f. satisfies A(x) = 1 + x*A(x) - x^2*A(x)^4.

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

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

%Y Cf. A343773, A367028, A367030.

%K sign

%O 0,4

%A _Seiichi Manyama_, Nov 02 2023