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A071660
Permutation of natural numbers induced by the automorphism robl_car_cdr! acting on the parenthesizations encoded by A014486.
12
0, 1, 3, 2, 6, 8, 7, 4, 5, 15, 14, 19, 20, 22, 16, 21, 17, 9, 10, 18, 11, 12, 13, 39, 41, 40, 37, 38, 52, 51, 53, 55, 54, 60, 61, 62, 64, 43, 42, 56, 57, 63, 44, 58, 45, 23, 24, 46, 25, 26, 27, 47, 59, 48, 28, 29, 49, 30, 31, 32, 50, 33, 34, 35, 36, 113, 112, 117, 118, 120
OFFSET
0,3
LINKS
A. Karttunen, Gatomorphisms (Includes the complete Scheme source for computing this sequence)
PROG
(Scheme function implementing this automorphism on list-structures:)
(define (robl_car_cdr! s) (cond ((not (pair? s))) ((not (pair? (cdr s))) (swap! s)) (else (robl! s) (robl_car_cdr! (car s)) (robl_car_cdr! (cdr s)))) s)
(define (robl! s) (let ((ex-car (car s))) (set-car! s (cddr s)) (set-cdr! (cdr s) ex-car) (swap! (cdr s)) (swap! s) s))
(define (swap! s) (let ((ex-car (car s))) (set-car! s (cdr s)) (set-cdr! s ex-car) s))
CROSSREFS
Inverse permutation: A071659. The car/cdr-flipped conjugate of A071655, i.e. A071660(n) = A057163(A071655(A057163(n))). Cf. also A071657, A071658.
Sequence in context: A072093 A130925 A089858 * A130393 A130956 A131001
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 30 2002
STATUS
approved