This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A381572 #12 Mar 02 2025 08:01:12 %S A381572 1,2,7,38,267,2232,21200,222556,2536661,31010886,403097573,5535291884, %T A381572 79900803514,1207657432714,19052200105025,312909670649562, %U A381572 5338325737985841,94422672774323512,1728653714036740230,32708138881741705812,638762549199936808759,12859693257887577375744 %N A381572 G.f. A(x) satisfies A(x) = 1/(1 - x*A(x*A(x)))^2. %F A381572 See A381571. %F A381572 G.f.: B(x)^2, where B(x) is the g.f. of A381029. %o A381572 (PARI) a(n, k=1) = if(k==0, 0^n, 2*k*sum(j=0, n, binomial(2*n-j+2*k, j)/(2*n-j+2*k)*a(n-j, j))); %Y A381572 Column k=1 of A381571. %Y A381572 Cf. A381029. %K A381572 nonn %O A381572 0,2 %A A381572 _Seiichi Manyama_, Feb 28 2025