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 A031248 #6 Aug 02 2016 10:25:22 %S A031248 1,0,0,0,0,1,2,3,2,3,3,4,4,5,5,4,5,4,3,2,2,1,1,0,0,0,1,1,0,0,0,0,0,0, %T A031248 0,0,1,1,0,0,0,0,0,0,0,0,1,2,2,3,2,2,3,3,3,4,4,4,5,5,6,7,8,9,10,9,10, %U A031248 11,11,12,13,13,14,15,15,14,15,16,15,16,15,14 %N A031248 a(n)=(# 1's)-(# 2's) in first n terms of A031235. %t A031248 Accumulate[Which[#==1,1,#==2,-1,True,0]&/@(Reverse[IntegerDigits[ #,5]]&/@ Range[ 0,40]//Flatten)] (* _Harvey P. Dale_, Aug 02 2016 *) %K A031248 nonn %O A031248 1,7 %A A031248 _Clark Kimberling_