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 A194040 #8 Mar 19 2022 00:24:13 %S A194040 1,3,6,2,5,9,10,4,8,13,14,15,7,12,18,19,20,21,11,17,24,25,26,27,28,16, %T A194040 23,31,32,33,34,35,36,22,30,39,40,41,42,43,44,45,29,38,48,49,50,51,52, %U A194040 53,54,55,37,47,58,59,60,61,62,63,64,65 %N A194040 Inverse permutation to A194038; contains every positive integer exactly once. %t A194040 (See A194038.) %Y A194040 A194038. %K A194040 nonn %O A194040 1,2 %A A194040 _Clark Kimberling_, Aug 12 2011