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 A026240 #4 Mar 30 2012 18:56:05 %S A026240 0,2,3,2,3,3,2,3,2,1,1,1,1,3,4,7,3,11,4,11,16,19,7,19,22,27,32,33,11, %T A026240 37,11,39,40,45,48,53,16,59,62,63,19,65,19,65,68,81,22,83,88,89,98,99, %U A026240 27,103,108,111,116,121,32,121,33,129,130,133 %N A026240 a(n) = |s(n) - n|, where s = A026239. %K A026240 nonn %O A026240 1,2 %A A026240 _Clark Kimberling_