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 A072636 #5 May 01 2014 02:43:28 %S A072636 0,1,2,3,5,6,4,9,11,18,21,17,66,70,7,8,10,35,41,12,33,131,139,261,274, %T A072636 258,4101,4117,22,65,69,1030,1090,81,1026,16390,16454,20,23,19,68,72, %U A072636 13,14,36,521,547,42,515,8201,8233,15,16,34,43,129,132,137,2059,2179 %N A072636 Permutation of natural numbers induced by reranking plane binary trees given in the standard lexicographic order (A014486) with an "arithmetic global ranking algorithm", using packA054238tr as the packing bijection N X N -> N. %H A072636 A. Karttunen, <a href="http://www.iki.fi/~kartturi/matikka/Nekomorphisms/gatomorf.htm">Gatomorphisms</a> %H A072636 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A072636 (Scheme functions below show the essential idea. For a complete source, follow the "Gatomorphisms" link.) %o A072636 (define A072636 (lexrank->arithrank-bijection packA054238tr)) %o A072636 (define (lexrank->arithrank-bijection packfun) (lambda (n) (rank-bintree (binexp->parenthesization (A014486 n)) packfun))) %o A072636 (define (rank-bintree bt packfun) (cond ((not (pair? bt)) 0) (else (1+ (packfun (rank-bintree (car bt) packfun) (rank-bintree (cdr bt) packfun)))))) %o A072636 (define (packA054238tr x y) (+ (A000695 y) (* 2 (A000695 x)))) %Y A072636 Inverse permutation: A072637. Cf. also A014486, A000695, A054238, A071651, A072634, A072646, A072656, A072658, A072644. %K A072636 nonn %O A072636 0,3 %A A072636 _Antti Karttunen_, Jun 02 2002