A381568 - OEIS

%I #14 Feb 28 2025 06:34:19

%S 1,2,5,22,126,884,7149,64688,641836,6888740,79203860,968503090,

%T 12525131474,170555767116,2436592516874,36409825487380,

%U 567612675812796,9211031425896752,155283809480528788,2714788300934206360,49140787009610861896,919625415852055598804,17768937720619971300781

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

%F See A381567.

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

%Y Column k=1 of A381567.

%Y Cf. A087949, A120970, A381570.

%K nonn,new

%O 0,2

%A _Seiichi Manyama_, Feb 28 2025