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 A130573 #5 Mar 30 2012 18:50:58 %S A130573 0,1,2,3,4,5,6,7,8,9,10,11,19,20,12,13,14,15,16,17,18,21,22,29,30,23, %T A130573 24,25,26,27,28,31,32,33,39,40,34,35,36,37,38,41,42,43,44,49,50,45,46, %U A130573 47,48,51,52,53,54,55,59,60,56,57,58,61,62,63,64,65,66,69,70,67,68,71,72 %N A130573 A130571(A130571(n)). %C A130573 Permutation of the natural numbers with inverse A130574; %C A130573 a(A130575(n)) = A130575(n). %H A130573 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %K A130573 nonn %O A130573 0,3 %A A130573 _Reinhard Zumkeller_, Jun 05 2007