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 A118142 #4 Aug 08 2015 23:57:24 %S A118142 4,5,9,11,16,19,23,29,30,32,33,39,47,59,61,62,64,65,67,79,84,95,101, %T A118142 119,123,125,126,128,129,131,135,154,159,164,169,170,185,191,203,204, %U A118142 239,247,251,253,254,256,257,259 %N A118142 Numbers n such that a perfect n X n parity pattern exists. %C A118142 See A118141 for definitions and references. %Y A118142 A subsequence of A117870. %K A118142 nonn %O A118142 1,1 %A A118142 _Don Knuth_, May 11 2006