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 A213435 #7 Jul 01 2019 10:03:59
%S A213435 1,1,2,6,32,620,259960,62059718088,3840971361624607057216,
%T A213435 14752998887519276350335088653216965113845136
%N A213435 G.f. A(x) = 1 / (1 - a(0)*x / (1 - a(1)*x / (1 - a(2)*x / ...))).
%H A213435 Vaclav Kotesovec, <a href="/A213435/b213435.txt">Table of n, a(n) for n = 0..13</a>
%e A213435 1 + x + 2*x^2 + 6*x^3 + 32*x^4 + 620*x^5 + 259960*x^6 + 62059718088*x^7 + ...
%o A213435 (PARI) {a(n) = local(A, y='y); if( n<0, 0, A = y; for( k=0, n, A = subst( A, y, 1 / (1 - x*y* subst( polcoeff( A + x*O(x^k), k), y, 1)))); simplify( polcoeff( A + x*O(x^n), n)))}
%K A213435 nonn
%O A213435 0,3
%A A213435 _Michael Somos_, Jun 11 2012