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 A072765 #6 May 01 2014 02:47:42 %S A072765 0,1,3,2,6,10,5,4,7,15,21,28,36,45,9,14,8,11,16,12,22,29,37,55,66,78, %T A072765 91,105,120,136,153,171,190,210,231,253,276,20,27,35,44,54,13,19,17, %U A072765 46,56,23,67,79,92,18,25,30,106,121,38,137,154,172,47,191,211,232,254,300 %N A072765 Inverse permutation to A072764. %H A072765 A. Karttunen, <a href="http://www.iki.fi/~kartturi/matikka/Nekomorphisms/gatomorf.htm">Gatomorphisms</a> (with the complete Scheme source) %H A072765 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A072765 (Scheme function showing the general idea:) (define (A072765 n) (cond ((zero? n) n) (else (1+ (packA001477 (A072771 n) (A072772 n)))))) %Y A072765 Cf. A072767, A001477, A072771, A072772. %K A072765 nonn %O A072765 0,3 %A A072765 _Antti Karttunen_, Jun 12 2002