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 A089865 #13 Jun 27 2012 13:54:21 %S A089865 0,1,2,3,4,5,6,8,7,9,10,11,12,13,14,15,19,20,21,16,22,17,18,23,24,25, %T A089865 26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,51,52,53,54,55,56,57, %U A089865 58,59,42,43,60,61,62,44,63,45,46,47,64,48,49,50,65,66,67,68,69 %N A089865 Permutation of natural numbers induced by Catalan Automorphism *A089865 acting on the parenthesizations/binary trees encoded by A014486/A063171. %C A089865 This bijection of binary trees is obtained when we apply bijection *A074679 to the left subtree and keep the right subtree intact. %C A089865 ....B...C.......A...B %C A089865 .....\./.........\./ %C A089865 ..A...x....-->....x...C.................A..().........()..A.... %C A089865 ...\./.............\./...................\./....-->....\./..... %C A089865 ....x...D...........x...D.................x...C.........x...C.. %C A089865 .....\./.............\./...................\./...........\./... %C A089865 ......x...............x.....................x.............x.... %C A089865 ............................................................... %C A089865 Compare to A154121. %C A089865 See "Catalan Automorphisms" OEIS-Wiki page for a detailed explanation how to obtain a given integer sequence from this definition. %H A089865 A. Karttunen, <a href="http://oeis.org/wiki/Catalan_Automorphisms">Catalan Automorphisms</a> %H A089865 A. Karttunen, <a href="/A089408/a089408.c.txt">C-program for computing this sequence</a> %H A089865 <a href="/index/Per#IntegerPermutationCatAuto">Index entries for signature-permutations induced by Catalan automorphisms</a> %o A089865 (Scheme function implementing this automorphism on list-structures/S-expressions, both constructive (*A089865) and destructive (*A089865!) versions:) %o A089865 (define (*A089865 s) (cond ((pair? s) (cons (*A074679 (car s)) (cdr s))) (else s))) %o A089865 (define (*A089865! s) (if (pair? s) (*A074679! (car s))) s) %Y A089865 Row 4207 of A089840. Inverse of A089866. a(n) = A069770(A154121(A069770(n))). %Y A089865 Number of cycles: A089844. Number of fixed-points: A005807 (prepended with two 1's). Max. cycle size: A089410. LCM of cycle sizes: A089845 (in each range limited by A014137 and A014138). %K A089865 nonn %O A089865 0,3 %A A089865 _Antti Karttunen_, Dec 20 2003 %E A089865 Further comments and constructive version of Scheme-implementation added by _Antti Karttunen_, Jun 04 2011