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 A031249 #4 Mar 30 2012 18:56:21 %S A031249 0,1,0,0,0,0,0,0,1,1,0,0,0,0,0,1,1,2,3,4,3,4,4,5,5,4,4,3,4,3,2,1,1,0, %T A031249 0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1, %U A031249 0,0,0,0,0,0,0,1,1,1,2,2,3,4,4,3,4,4,4,5,5,5 %N A031249 a(n)=(# 2's)-(# 3's) in first n terms of A031235. %K A031249 nonn %O A031249 1,18 %A A031249 _Clark Kimberling_