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 A066250 #6 Mar 30 2012 18:50:19 %S A066250 1,3,2,5,4,7,6,8,10,9,12,11,14,16,18,13,20,15,22,24,26,17,28,30,32,34, %T A066250 36,19,38,21,40,42,44,46,48,23,50,52,54,25,56,27,58,60,62,29,64,66,68, %U A066250 70,72,31,74,76,78,80,82,33,84,35,86,88,90,92,94,37,96,98,100,39,102 %N A066250 a(n) = if n+1 is prime then A049084(n+1)*2 - 1 else A066246(n+1)*2. %C A066250 Permutation of natural numbers; inverse: A066251. %H A066250 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A066250 a(n) = A026238(n+1)*2 - A010051(n+1). %Y A066250 Cf. A066251, A049084, A066246, A026238, A010051, A066248, A066254. %K A066250 nonn %O A066250 1,2 %A A066250 _Reinhard Zumkeller_, Dec 09 2001