id:A069771 - OEIS Search Results

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Self-inverse permutation of natural numbers induced by the automorphism RotateHandshakes180 acting on the parenthesizations encoded by A014486.

+0
11

0, 1, 2, 3, 7, 5, 6, 4, 8, 9, 14, 21, 18, 13, 10, 15, 20, 17, 12, 19, 16, 11, 22, 45, 54, 31, 26, 40, 44, 53, 30, 25, 39, 63, 59, 50, 36, 46, 55, 32, 27, 41, 42, 51, 28, 23, 37, 62, 58, 49, 35, 43, 52, 29, 24, 38, 61, 57, 48, 34, 60, 56, 47, 33, 64, 65, 79, 107, 121, 149, 170 (list; graph; listen)

	OFFSET	`0,3`
	COMMENT	`This automorphism rotates by 180 degrees the intepretation n (the non-crossing handshakes) of Stanley's exercise 19.`
	LINKS	`A. Karttunen, Gatomorphisms (Includes the complete Scheme program for computing this sequence)` `R. P. Stanley, Exercises on Catalan and Related Numbers` `Index entries for sequences that are permutations of the natural numbers`
	PROGRAM	`(Scheme function implementing this automorphism on list-structures:) (define (RotateHandshakes180 a) (RotateHandshakes_n_steps a (count-pars a)))` `(define (count-pars a) (if (not (pair? a)) 0 (+ 1 (count-pars (car a)) (count-pars (cdr a)))))` `(define (RotateHandshakes a) (if (null? a) (list) (append (car a) (list (cdr a)))))` `(define (RotateHandshakes_n_steps a n) (if (zero? n) a (RotateHandshakes_n_steps (RotateHandshakes a) (-1+ n))))`
	CROSSREFS	`Cf. A057501, A069772, A069888, A069889.` `Sequence in context: A082734 A021425 A060940 this_sequence A076986 A069786 A128804` `Adjacent sequences: A069768 A069769 A069770 this_sequence A069772 A069773 A069774`
	KEYWORD	`nonn`
	AUTHOR	`Antti Karttunen Apr 16 2002`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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