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 A072009 #4 Sep 04 2014 16:41:14 %S A072009 0,1,4,2,7,10,3,5,13,16,19,22,8,6,25,28,11,31,34,37,40,9,14,43,46,49, %T A072009 17,52,12,55,20,58,61,64,23,67,70,15,73,76,26,79,82,85,18,29,88,91,94, %U A072009 32,97,21,100,35,103,106,109,38,24,112,115,41 %N A072009 Inverse of permutation A072007. %H A072009 Reinhard Zumkeller, <a href="/A072009/b072009.txt">Table of n, a(n) for n = 0..10000</a> %Y A072009 Cf. A072007. %K A072009 nonn %O A072009 0,3 %A A072009 _Clark Kimberling_, Jun 07 2002