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 A072740 #3 May 01 2014 02:47:42 %S A072740 0,1,0,2,0,0,4,3,0,0,6,5,1,0,0,8,7,2,1,0,0,10,9,3,1,1,0,0,12,11,5,4,1, %T A072740 1,0,0,14,13,7,6,2,1,1,0,0,16,15,9,8,3,2,1,1,0,0,18,17,11,10,4,2,2,1, %U A072740 1,0,0,20,19,13,12,6,5,2,2,1,1,0,0,22,21,15,14,8,7,3,2,2,1,1,0,0,24,23 %N A072740 X-projection of the tabular N X N -> N bijection A072734. %o A072740 (Scheme) (define (A072740 n) (A025581 (A072735 n))) %Y A072740 The Y-projection is A072741. Composition of A025581 and A072735. A072783(n) = A072740(n)-A072736(n). %K A072740 nonn,tabl %O A072740 0,4 %A A072740 _Antti Karttunen_, Jun 12 2002