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 A162503 #4 Mar 30 2012 18:51:04 %S A162503 1,30,31,14,10,16,6,4,11,80,81,40,12,23,32,41,2,28,82,15,20,35,53,5, %T A162503 21,300,301,50,13,48,84,51,3,57,75,67,76,68,60,61,19,17,24,7,29,70,36, %U A162503 71,104,18,49,8,58,118,808,86,9,90,42,91,92,100,63,101,44,102,94,22,85,719 %N A162503 A162501(A162501(n)). %C A162503 Inverse of A162504: a(A162504(n)) = A162504(a(n)) = n; %C A162503 A162501(n) = A162502(a(n)) = a(A162502(n)). %H A162503 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %K A162503 nonn %O A162503 1,2 %A A162503 _Reinhard Zumkeller_, Jul 05 2009