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 A072090 Permutation of natural numbers induced by the automorphism cdr_robr_car! acting on the parenthesizations encoded by A014486. 7
 0, 1, 3, 2, 7, 8, 4, 5, 6, 17, 18, 20, 21, 22, 10, 9, 11, 12, 13, 14, 15, 19, 16, 45, 46, 48, 49, 50, 54, 55, 57, 58, 59, 61, 62, 63, 64, 26, 27, 23, 24, 25, 29, 28, 30, 31, 32, 33, 34, 35, 36, 38, 37, 39, 40, 41, 51, 52, 56, 60, 42, 43, 44, 47, 53, 129, 130, 132, 133, 134 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS A. Karttunen, Gatomorphisms (Includes the complete Scheme program for computing this sequence) PROG (Scheme function implementing this automorphism on list-structures:) (define (cdr_robr_car! s) (cond ((not (pair? s))) ((not (pair? (car s))) (swap! s)) (else (cdr_robr_car! (cdr s)) (robr! s) (cdr_robr_car! (car s)))) s) (define (robr! s) (let ((ex-cdr (cdr s))) (set-cdr! s (caar s)) (set-car! (car s) ex-cdr) (swap! (car 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: A072091 and also its car/cdr-flipped conjugate, i.e. A072090(n) = A057163(A072091(A057163(n))). Cf. also A071655-A071660, A072092-A072095. Sequence in context: A074680 A123496 A130370 * A130365 A130933 A130966 Adjacent sequences:  A072087 A072088 A072089 * A072091 A072092 A072093 KEYWORD nonn AUTHOR Antti Karttunen, Jun 25 2002 STATUS approved

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Last modified October 14 14:06 EDT 2019. Contains 328017 sequences. (Running on oeis4.)