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 A143693 #5 Mar 30 2012 18:51:00 %S A143693 1,2,3,4,5,6,10,9,8,7,12,14,16,11,13,15,24,21,19,17,20,22,26,18,23,25, %T A143693 36,33,30,27,38,34,31,28,32,35,40,29,37,39,43,46,55,41,56,49,48,42,58, %U A143693 51,50,54,60,44,52,45,53,47,59,57,61,62,69,64,77,65,70,63,85,74,87,66 %N A143693 A143691(A143691(n)). %C A143693 Permutation of the natural numbers with inverse A143694. %H A143693 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %K A143693 nonn %O A143693 1,2 %A A143693 _Reinhard Zumkeller_, Aug 29 2008