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 A167904 #4 Mar 30 2012 18:51:05 %S A167904 1,2,3,4,5,6,7,8,9,10,11,12,16,14,13,15,17,18,19,20,21,22,23,24,27,28, %T A167904 25,26,29,30,33,34,31,32,35,36,37,39,40,38,41,42,43,44,45,46,47,48,49, %U A167904 51,52,50,53,54,55,56,57,58,60,59,62,61,63,64,65,66,67,69,70,68,71,72 %N A167904 A121878(A121878(n)). %C A167904 Permutation of positive integers; %C A167904 a(A167906(n)) = A167906(n); %C A167904 a(A167905(n)) = A167905(a(n)) = A121878(n). %H A167904 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %K A167904 nonn %O A167904 1,2 %A A167904 _Reinhard Zumkeller_, Nov 15 2009