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 A031231 #4 Mar 30 2012 18:56:21 %S A031231 1,1,1,1,2,1,2,3,4,4,5,5,6,6,6,5,5,6,6,6,6,6,6,6,6,5,5,6,6,6,6,6,6,6, %T A031231 6,5,5,6,6,6,6,6,6,6,7,6,5,6,5,6,7,6,6,7,6,6,7,6,6,7,8,7,8,9,10,11,12, %U A031231 12,13,14,14,15,16,16,17,17,16,17,17,18,19,19 %N A031231 (# 1's)-(# 0's) in first n terms of A031219. %K A031231 nonn %O A031231 1,5 %A A031231 _Clark Kimberling_