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 A109721 #8 Dec 13 2015 17:40:38 %S A109721 1,3,21,77,252,567,1051,1465,1674,1465,1051,567,252,77,21,3,1 %N A109721 Number of different ways of selecting n nonempty cells in a 4 X 4 binary matrix, excluding all rotationally and symmetrically equivalent matrices. %Y A109721 A row of A054252. %K A109721 nonn,fini,full %O A109721 0,2 %A A109721 _Philippe Beaudoin_, Aug 09 2005