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 A194870 #9 Jul 10 2019 01:49:42 %S A194870 1,3,2,5,4,6,8,10,7,9,15,12,14,11,13,20,17,19,16,21,18,26,23,28,25,22, %T A194870 27,24,36,33,30,35,32,29,34,31,44,41,38,43,40,37,45,42,39,53,50,47,55, %U A194870 52,49,46,54,51,48,63,60,57,65,62,59,56,64,61,58,66,74,71,68 %N A194870 Inverse permutation of A194869; every positive integer occurs exactly once. %t A194870 (See A194868.) %Y A194870 Cf. A194868, A194869. %K A194870 nonn %O A194870 1,2 %A A194870 _Clark Kimberling_, Sep 04 2011