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 A066252 #6 Mar 30 2012 18:50:19 %S A066252 4,6,2,8,1,7,3,5,9,10,11,12,13,17,19,15,21,14,25,27,31,16,35,37,39,43, %T A066252 47,23,49,18,53,55,57,61,63,29,67,71,73,33,77,20,81,83,85,22,89,93,95, %U A066252 99,101,41,103,107,111,113,117,45,119,24,123,127,129,133,137,51,141 %N A066252 a(n) = A066248(A066248(n)). %C A066252 Permutation of natural numbers. %H A066252 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %K A066252 nonn %O A066252 1,1 %A A066252 _Reinhard Zumkeller_, Dec 09 2001