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 A026190 #4 Mar 30 2012 18:56:05 %S A026190 2,1,4,6,7,3,10,12,13,5,16,18,19,21,22,8,25,9,28,30,31,11,34,36,37,39, %T A026190 40,14,43,15,46,48,49,17,52,54,55,57,58,20,61,63,64,66,67,23,70,24,73, %U A026190 75,76,26,79,27,82,84,85,29,88,90,91,93,94 %N A026190 a(n) = (1/2)*s(n), where s(n) is the n-th even number in A026142. %K A026190 nonn %O A026190 1,1 %A A026190 _Clark Kimberling_