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 A210771 #8 Jul 13 2013 12:04:25 %S A210771 1,2,4,6,3,8,5,10,12,7,14,16,18,9,20,22,11,24,26,13,28,30,15,32,17,34, %T A210771 36,19,38,40,21,42,44,23,46,48,25,50,52,27,54,56,29,58,60,31,62,64,66, %U A210771 33,68,70,35,72,74,37,76,78,39,80,82,41,84,86,43,88,90 %N A210771 Inverse permutation to A210770. %H A210771 Reinhard Zumkeller, <a href="/A210771/b210771.txt">Table of n, a(n) for n = 1..10000</a> %H A210771 <a href="/index/Per#IntegerPermutation"> Index entries for sequences that are permutations of the natural numbers</a> %o A210771 (Haskell) %o A210771 import Data.List (elemIndex) %o A210771 import Data.Maybe (fromJust) %o A210771 a210771 n = fromJust (elemIndex n a210770_list) + 1 %K A210771 nonn %O A210771 1,2 %A A210771 _Reinhard Zumkeller_, Mar 25 2012