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 A038393 #6 Mar 30 2012 18:35:34 %S A038393 1,1,2,6,20,78,342,1608,7966,41054,218342,1191038,6635164,37621952, %T A038393 216557220,1262829914,7447921572 %N A038393 Number of 4n-step self-avoiding closed paths on first quadrant grid, passing through origin, symmetric about line y = x. %Y A038393 Cf. A034010. %K A038393 nonn %O A038393 0,3 %A A038393 _David W. Wilson_