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 A026259 #4 Mar 30 2012 18:56:05 %S A026259 1,2,3,7,4,8,9,5,6,13,14,15,10,20,11,21,22,12,26,27,28,16,17,33,18,34, %T A026259 35,19,39,40,41,23,24,46,25,47,52,53,54,29,30,31,59,32,60,65,66,67,36, %U A026259 37,38,72,73,78,42,79,80,43,44,45,85,86,48 %N A026259 a(n) = (1/2)*s(n), where s(n) is the n-th even number in A026255. %K A026259 nonn %O A026259 1,2 %A A026259 _Clark Kimberling_