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 A259570 #4 Jun 30 2015 15:20:49 %S A259570 1,2,4,3,5,6,8,7,9,12,10,11,13,14,16,15,17,18,20,19,21,22,24,25,23,27, %T A259570 30,26,29,28,31,32,34,33,35,36,38,37,40,41,39,44,42,43,45,48,46,47,49, %U A259570 51,53,52,50,56,54,55,57,58,60,61,59,65,62,67,63,64,68 %N A259570 Smallest m such that A259565(m) = 2*n-1. %C A259570 Sequence is a permutation of the natural numbers iff A259565 is a permutation of the odd numbers; %C A259570 A259565(a(n)) = 2*n-1. %H A259570 Reinhard Zumkeller, <a href="/A259570/b259570.txt">Table of n, a(n) for n = 1..10000</a> %o A259570 (Haskell) %o A259570 import Data.List (elemIndex); import Data.Maybe (fromJust) %o A259570 a259570 = (+ 1) . fromJust . (`elemIndex` a259565_list) . subtract 1 . (* 2) %Y A259570 Cf. A259565. %K A259570 nonn %O A259570 1,2 %A A259570 _Reinhard Zumkeller_, Jun 30 2015