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 A086572 #8 Mar 30 2012 18:50:37 %S A086572 2,1,9,6,10,4,14,12,3,5,22,8,26,7,45,32,34,24,38,30,63,11,46,18,50,13, %T A086572 36,42,58,20,62,16,99,17,70,27,74,19,117,100,82,28,86,66,15,23,94,60, %U A086572 98,25,153,78,106,72,110,84,171,29,118,48,122,31,21,80,130,44,134 %N A086572 Solution to A086571(a(n))=A086571(n) and a(n)<>n. %C A086572 Well defined as each number occurs exactly twice in A086571; %C A086572 a self-inverse permutation of natural numbers: a(a(n))=n. %C A086572 A086938(n) = a(A086939(n)), A086939(n) = a(A086938(n)). - _Reinhard Zumkeller_, Jul 24 2003 %H A086572 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %e A086572 A086571(8)=4 and A086571(12)=4, therefore a(8)=12 and a(12)=8. %K A086572 nonn %O A086572 1,1 %A A086572 _Reinhard Zumkeller_, Jul 22 2003