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 A066251 #6 Mar 30 2012 18:50:19 %S A066251 1,3,2,5,4,7,6,8,10,9,12,11,16,13,18,14,22,15,28,17,30,19,36,20,40,21, %T A066251 42,23,46,24,52,25,58,26,60,27,66,29,70,31,72,32,78,33,82,34,88,35,96, %U A066251 37,100,38,102,39,106,41,108,43,112,44,126,45,130,47,136,48,138,49,148 %N A066251 Inverse permutation to A066250. %C A066251 Permutation of natural numbers. %H A066251 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A066251 a(n) = (if n is odd then A000040((n+1)/2) else A002808(n/2)) - 1. %Y A066251 Cf. A066250, A000040, A002808, A066248, A066255. %K A066251 nonn %O A066251 1,2 %A A066251 _Reinhard Zumkeller_, Dec 09 2001