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 A185757 #4 Mar 30 2012 18:37:26
%S A185757 6,120,2340,49315,1142932,29141994,814059798,24779916843,817506518829,
%T A185757 29081010732059,1110248649302494,45298134089851175,
%U A185757 1967550159430960784,90668183653348456484,4418855084158930131012,227122154996245283660487
%N A185757 Column 2 of triangle A185755.
%C A185757 A185755(n,k) equals the coefficient of x^n*y^k in the n-th iteration of x*(1+xy)/(1-x).
%o A185757 (PARI) {a(n)=local(A=x, G=x*(1+x*y)/(1-x)); for(i=1, n+2, A=subst(G, x, A+O(x^(n+3))));polcoeff(polcoeff(A, n+2,x),2,y)}
%Y A185757 Cf. A185755, A185756, A185758, A185759.
%K A185757 nonn
%O A185757 1,1
%A A185757 _Paul D. Hanna_, Feb 03 2011