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 A031247 #4 Mar 30 2012 18:56:21 %S A031247 1,1,1,1,0,1,2,3,3,4,4,5,5,6,5,5,6,6,6,6,6,6,6,6,5,5,6,6,6,6,6,6,6,6, %T A031247 5,5,6,6,6,6,6,6,6,6,5,4,5,6,5,6,6,5,6,6,5,6,6,5,6,5,6,7,8,9,10,10,11, %U A031247 12,12,13,14,14,15,16,15,15,16,17,17,18,18,18 %N A031247 a(n)=(# 1's)-(# 0's) in first n terms of A031235. %K A031247 nonn %O A031247 1,7 %A A031247 _Clark Kimberling_