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 A140422 #5 Mar 31 2012 12:35:07 %S A140422 1,5,47,849,29241,1901849,234932757,55047807551,24470603864937, %T A140422 20637055514911557,33018065501295740951,100220335496292824426843, %U A140422 577112450349963078523926227 %N A140422 Half the number of n X n symmetric binary matrices with every 1 adjacent to some 0 horizontally or vertically and every 0 adjacent to some 1 horizontally or vertically. %K A140422 nonn %O A140422 2,2 %A A140422 _R. H. Hardin_, Jun 18 2008