A085169 - OEIS

A085169

Permutation of natural numbers induced by the Catalan bijection gma085169 acting on symbolless S-expressions encoded by A014486/A063171.

0, 1, 2, 3, 4, 5, 6, 8, 7, 9, 10, 11, 13, 12, 14, 15, 19, 22, 21, 16, 18, 17, 20, 23, 24, 25, 27, 26, 28, 29, 33, 36, 35, 30, 32, 31, 34, 37, 38, 39, 41, 40, 51, 52, 60, 64, 63, 56, 59, 58, 62, 42, 43, 47, 50, 49, 44, 46, 45, 48, 53, 55, 54, 61, 57, 65, 66, 67, 69, 68

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OFFSET

0,3

COMMENTS

A parenthesization is fixed by the Catalan bijections A085169/A085170 if and only if no other elements than () and (()) occur at its top-level: (); ()(),(()); ()()(),()(()),(())(); ()()()(),()()(()),()(())(),(())()(),(())(()); ... There is a simple bijection between these and Zeckendorf-expansions, explaining why Fibonacci numbers gives the number of fixed points of this permutation.

In addition to "rising slope" and "descending slope" mappings from Dyck paths to noncrossing Murasaki-diagrams as illustrated in A085161 and A086431 there is also a mapping where we insert a vertical stick after every second parenthesis and connect those that are on the same level without any intermediate points below. This Catalan bijection converts between these two mappings. See the illustration at example lines.

LINKS

Table of n, a(n) for n=0..69.

A. Karttunen, Gatomorphisms (With the complete Scheme source)

Index entries for signature-permutations induced by Catalan automorphisms

EXAMPLE

.........................

..._____....________.....

..|.....|..|.....|..|....

..|..|..|..|..|..|..|....

..1((2))3((4((5))6()7))..

...(())(((())()))........

...11001111001000=13256=A014486(368)

To obtain the same Murasaki diagram using the "rising slope mapping" illustrated in A085161, we should use the following Dyck path, encoded by 360th binary string in A014486/A063171:

....___.._____...........

...|...||...|.|..........

...||..|||..|.|..........

...||..||/\.|.|..........

...|/\.|/..\/\/\.........

.../..\/........\........

...11001110010100=13204=A014486(360)

So we have A085169(368)=360 and A085170(360)=368.

PROG

(Scheme function implementing this automorphism on list-structures:)

(define (gma085169 s) (letrec ((evenlev (lambda (s) (cond ((not (pair? s)) s) (else (cons (oddlev (car s)) (evenlev (cdr s))))))) (oddlev (lambda (s) (cond ((not (pair? s)) s) (else (append (evenlev (car s)) (list (oddlev (cdr s))))))))) (evenlev s)))

CROSSREFS

Inverse: A085170. a(n) = A086433(A082853(n))+A082852(n). A074684 = A083925(A085169(A057548(n))). Cf. also A085159, A085160, A085175.

Number of cycles: A086585. Number of fixed points: A000045. Max. cycle size: A086586. LCM of cycle sizes: A086587. (In range [A014137(n-1)..A014138(n-1)] of this permutation).

Sequence in context: A127380 A122350 A127381 * A127379 A073289 A122349

Adjacent sequences: A085166 A085167 A085168 * A085170 A085171 A085172

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jun 23 2003

STATUS

approved