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 A072772 #3 May 01 2014 02:47:42 %S A072772 0,1,0,2,3,1,0,0,4,5,6,7,8,2,3,1,0,0,1,0,0,0,9,10,11,12,13,14,15,16, %T A072772 17,18,19,20,21,22,4,5,6,7,8,2,3,1,0,0,1,0,0,0,2,3,1,0,0,1,0,0,0,1,0, %U A072772 0,0,0,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44 %N A072772 Y-projection of the tabular N X N -> N bijection A072764 and X-projection of its transpose A072766. %C A072772 This corresponds to Lisp/Scheme function 'cdr' computed with respect to the lexicographical ordering of parenthesizations/planar binary trees (A014486), i.e. with planar binary trees this is equal to extracting the right subtree (from the root), with general parenthesizations equal to discarding the first sub-parenthesization of the top-level list and with general plane trees equal to discarding the leftmost branch from the root. %H A072772 A. Karttunen, <a href="http://www.iki.fi/~kartturi/matikka/Nekomorphisms/gatomorf.htm">Gatomorphisms</a> (with the complete Scheme source) %K A072772 nonn %O A072772 1,4 %A A072772 _Antti Karttunen_, Jun 12 2002