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 A026143 #4 Mar 30 2012 18:56:04 %S A026143 1,3,5,2,8,9,11,4,14,15,17,6,20,7,23,24,26,27,29,10,32,33,35,12,38,13, %T A026143 41,42,44,45,47,16,50,51,53,18,56,19,59,60,62,21,65,22,68,69,71,72,74, %U A026143 25,77,78,80,81,83,28,86,87,89,30,92,31,95,96,98,99,101,34,104 %N A026143 a(n) = position of n in A026142. %K A026143 nonn %O A026143 1,2 %A A026143 _Clark Kimberling_