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 A118143 #10 Jan 12 2020 14:43:45 %S A118143 4,5,11,16,23,29,30,32,47,59,62,64,65,84,95,101,119,125,126,128,131, %T A118143 154,164,170,185,191,203,204,239,251,254,256,257 %N A118143 Numbers n for which there exists a perfect n X n parity pattern with 8-fold symmetry. %C A118143 See A118141 for definitions and references. %C A118143 If an odd number m appears then so does 2m+1. %Y A118143 Cf. A118141. %K A118143 nonn,more %O A118143 1,1 %A A118143 _Don Knuth_, May 11 2006