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 A194840 #5 Mar 30 2012 18:57:44 %S A194840 1,3,2,6,5,4,9,8,7,10,13,12,15,11,14,18,21,17,20,16,19,28,24,27,23,26, %T A194840 22,25,35,31,34,30,33,29,36,32,43,39,42,38,45,41,37,44,40,52,48,55,51, %U A194840 47,54,50,46,53,49,66,62,58,65,61,57,64,60,56,63,59,77,73,69 %N A194840 Inverse permutation of A194839; every positive integer occurs exactly once. %t A194840 (See A194839.) %Y A194840 Cf. A194838, A194839, A194832. %K A194840 nonn %O A194840 1,2 %A A194840 _Clark Kimberling_, Sep 03 2011