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 A026247 #4 Mar 30 2012 18:56:05 %S A026247 1,5,2,3,9,10,4,13,14,6,17,18,7,8,22,26,27,11,30,31,12,34,35,39,15,16, %T A026247 43,47,48,19,51,52,20,21,56,60,23,24,64,65,25,68,69,73,28,29,77,81,82, %U A026247 32,85,86,33,89,90,94,36,37,98,99,38,102,103 %N A026247 a(n) = (1/2)*s(n), where s(n) is n-th even number in A002251. %K A026247 nonn %O A026247 1,2 %A A026247 _Clark Kimberling_