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 A190131 #11 Jul 13 2013 12:04:08 %S A190131 1,4682,7076,7661,8246,8831,9416,2,587,1172,1757,2342,2927,3512,4097, %T A190131 4683,5268,5853,6438,6784,6857,6930,7003,7077,7150,7223,7296,7369, %U A190131 7442,7515,7588,7662,7735,7808,7881,7954,8027,8100,8173,8247,8320,8393,8466,8539 %N A190131 Inverse permutation to A190130. %C A190131 a(A190128(n)) = A190128(a(n)) = n. %H A190131 Reinhard Zumkeller, <a href="/A190131/b190131.txt">Table of n, a(n) for n = 1..10000</a> (full sequence) %o A190131 (Haskell) %o A190131 import Data.List (elemIndex) %o A190131 import Data.Maybe (fromJust) %o A190131 a190131 n = a190131_list !! (n-1) %o A190131 a190131_list = %o A190131 map (succ . fromJust . (`elemIndex` a190130_list)) [1..10000] %K A190131 nonn,base,fini,full %O A190131 1,2 %A A190131 _Reinhard Zumkeller_, May 06 2011