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A089859
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Permutation of natural numbers induced by Catalan Automorphism *A089859 acting on the binary trees/parenthesizations encoded by A014486/A063171.
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21
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0, 1, 3, 2, 8, 7, 6, 4, 5, 21, 22, 20, 17, 18, 19, 16, 14, 9, 10, 15, 11, 12, 13, 58, 59, 62, 63, 64, 57, 61, 54, 45, 46, 55, 48, 49, 50, 56, 60, 53, 44, 47, 51, 42, 37, 23, 24, 38, 25, 26, 27, 52, 43, 39, 28, 29, 40, 30, 31, 32, 41, 33, 34, 35, 36, 170, 171, 174, 175, 176, 184
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OFFSET
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0,3
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COMMENTS
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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...-->... .x...A...............A..().........()..A..
....\./.............\./.................\./....-->....\./...
.....x...............x...................x.............x....
(a . (b . c)) --> ((c . b) . a) _____ (a . ()) --> (() . a)
See the Karttunen OEIS-Wiki link for a detailed explanation of how to obtain a given integer sequence from this definition.
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LINKS
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PROG
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(Scheme functions implementing this automorphism on list-structures/S-expressions, both constructive (*A089859) and destructive (*A089859!) versions:)
(define (*A089859 s) (cond ((not (pair? s)) s) ((not (pair? (cdr s))) (cons (cdr s) (car s))) (else (cons (cons (cddr s) (cadr s)) (car s)))))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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A graphical description and constructive implementation of Scheme-function (*A089859) added by Antti Karttunen, Jun 04 2011
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STATUS
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approved
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