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

%I #11 Sep 16 2023 10:42:00

%S 1,1,1,2,7,23,72,238,831,2959,10645,38824,143492,535700,2016020,

%T 7641574,29152015,111841263,431209723,1669945778,6493144143,

%U 25338440143,99204579648,389570145288,1534026813892,6055885764548,23962654178012,95023123291680

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

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

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

%Y Cf. A101785, A365244, A365693.

%Y Cf. A365690.

%K nonn

%O 0,4

%A _Seiichi Manyama_, Sep 16 2023