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 A130574 #5 Mar 30 2012 18:50:58 %S A130574 0,1,2,3,4,5,6,7,8,9,10,11,14,15,16,17,18,19,20,12,13,21,22,25,26,27, %T A130574 28,29,30,23,24,31,32,33,36,37,38,39,40,34,35,41,42,43,44,47,48,49,50, %U A130574 45,46,51,52,53,54,55,58,59,60,56,57,61,62,63,64,65,66,69,70,67,68,71,72 %N A130574 A130572(A130572(n)). %C A130574 Permutation of the natural numbers with inverse A130573; %C A130574 a(A130575(n)) = A130575(n). %H A130574 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %K A130574 nonn %O A130574 0,3 %A A130574 _Reinhard Zumkeller_, Jun 05 2007