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 A089850 Involution of natural numbers induced by Catalan automorphism *A089850 acting on the binary trees/parenthesizations encoded by A014486/A063171. 16
 0, 1, 2, 3, 5, 4, 6, 7, 8, 12, 13, 11, 9, 10, 15, 14, 16, 17, 18, 19, 20, 21, 22, 31, 32, 34, 35, 36, 30, 33, 28, 23, 24, 29, 25, 26, 27, 40, 41, 39, 37, 38, 43, 42, 44, 45, 46, 47, 48, 49, 50, 52, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 87, 88, 90, 91, 92, 96, 97, 99 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS This automorphism effects the following transformation on the unlabeled rooted plane binary trees (letters A, B, C refer to arbitrary subtrees located on those nodes and () stands for an implied terminal node.) ...B...C...........C...B ....\./.............\./ .A...x....-->....A...x.................A..().........A...().. ..\./.............\./...................\./....-->....\./... ...x...............x.....................x.............x.... (a . (b . c)) -> (a . (c . b)) ______ (a . ()) ---> (a . ()) In terms of S-expressions, this automorphism swaps cadr and cddr of an S-exp if its length > 1. Look at the example in A069770 to see how this will produce the given sequence of integers. LINKS A. Karttunen, Catalan Automorphisms A. Karttunen, C-program for computing this sequence PROG (Scheme functions implementing this automorphism on list-structures/S-expressions, constructive (*A089850) and destructive (*A089850!) version:) (define (*A089850 s) (if (and (pair? s) (pair? (cdr s))) (cons (car s) (cons (cddr s) (cadr s))) s)) (define (*A089850! s) (cond ((not (pair? s)) s) ((not (pair? (cdr s))) s) (else (*A069770! (cdr s)) s))) CROSSREFS a(n) = A069770(A089859(n)) = A089863(A069770(n)) = A057163(A089854(A057163(n))). Row 3 of A089840. Row 3771 of A122203 and row 3677 of A122204. Number of cycles: A073191. Number of fixed points: A073190. Max. cycle size & LCM of all cycle sizes: A046698 (in each range limited by A014137 and A014138). Sequence in context: A154121 A130375 A154122 * A154450 A154449 A122304 Adjacent sequences:  A089847 A089848 A089849 * A089851 A089852 A089853 KEYWORD nonn AUTHOR Antti Karttunen, Nov 29 2003 EXTENSIONS The new mail-address, a graphical explanation and constructive implementation of Scheme-function (*A089850) added by Antti Karttunen, Jun 04 2011 STATUS approved

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Last modified December 6 14:44 EST 2019. Contains 329806 sequences. (Running on oeis4.)