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 A072656 #5 May 01 2014 02:43:29 %S A072656 0,1,3,2,11,6,5,7,4,100,27,24,45,14,18,10,13,62,17,8,15,28,9,1988,477, %T A072656 179,1100,116,150,61,113,2090,147,35,189,302,58,162,44,39,73,23,34,20, %U A072656 102,1229,295,29,111,680,72,21,12,26,93,38,47,70,1292,91,16,22,117,187 %N A072656 Permutation of natural numbers induced by reranking plane binary trees given in the standard lexicographic order (A014486) with an "arithmetic global ranking algorithm", using packA048680oA054238 as the packing bijection N X N -> N. %H A072656 A. Karttunen, <a href="http://www.iki.fi/~kartturi/matikka/Nekomorphisms/gatomorf.htm">Gatomorphisms</a> %H A072656 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A072656 (Scheme functions below show the essential idea. For a complete source, follow the "Gatomorphisms" link.) %o A072656 (define A072656 (lexrank->arithrank-bijection packA048680oA054238)) %o A072656 (define (lexrank->arithrank-bijection packfun) (lambda (n) (rank-bintree (binexp->parenthesization (A014486 n)) packfun))) %o A072656 (define (rank-bintree bt packfun) (cond ((not (pair? bt)) 0) (else (1+ (packfun (rank-bintree (car bt) packfun) (rank-bintree (cdr bt) packfun)))))) %o A072656 (define (packA048680oA054238 x y) (A048680 (packA054238 x y))) %o A072656 (define (packA054238 x y) (+ (A000695 x) (* 2 (A000695 y)))) %Y A072656 Inverse permutation: A072657. Cf. also A014486, A000695, A054238, A048680, A071651, A072634, A072636, A072646, A072658, A072660. %K A072656 nonn %O A072656 0,3 %A A072656 _Antti Karttunen_, Jun 02 2002