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 A250553 #4 Dec 10 2014 23:59:03 %S A250553 1,2,3,4,5,7,9,13,6,8,11,15,10,12,14,17,19,16,18,21,23,25,20,22,27,29, %T A250553 31,33,35,26,37,28,24,30,39,32,34,41,43,36,38,45,40,42,44,46,47,48,49, %U A250553 50,51,55,52,53,57,54,56,59,61,58,60,63,65,62,66,64,68 %N A250553 Inverse permutation to A250552. %H A250553 Reinhard Zumkeller, <a href="/A250553/b250553.txt">Table of n, a(n) for n = 1..10000</a> %H A250553 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A250553 (Haskell) %o A250553 import Data.List (elemIndex); import Data.Maybe (fromJust) %o A250553 a250553 = (+ 1) . fromJust . (`elemIndex` a250552_list) %Y A250553 Cf. A250552 (inverse), A247204 (fixed points). %K A250553 nonn %O A250553 1,2 %A A250553 _Reinhard Zumkeller_, Dec 10 2014