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 A099258 #6 Mar 30 2012 18:50:48 %S A099258 1,3,2,4,6,7,8,9,5,10,12,13,14,15,16,17,18,19,20,21,11,22,24,25,26,27, %T A099258 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,23,46,48,49,50, %U A099258 51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73 %N A099258 Inverse of A099257. %C A099258 Permutation of the natural numbers; %C A099258 a(A033484(n)) = A033484(n); %C A099258 a(A033484(n) - 1) = A033484(n)/2 = A055010(n). %H A099258 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A099258 a(n) = if n = 3*2^k - 2 then n else (if n = 3*2^k - 3 then (n + 1)/2 else n + 1). %K A099258 nonn %O A099258 1,2 %A A099258 _Reinhard Zumkeller_, Oct 09 2004