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A130375
Signature permutation of a Catalan automorphism: apply *A074685 after the first nil on the top-level of list, if any present, otherwise leave the structure intact.
4
0, 1, 2, 3, 5, 4, 6, 7, 8, 11, 12, 13, 10, 9, 14, 15, 16, 17, 18, 19, 20, 21, 22, 29, 28, 30, 31, 32, 33, 34, 35, 25, 26, 36, 27, 24, 23, 38, 37, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 81, 82, 83, 80, 79, 85, 84
OFFSET
0,3
PROG
(Destructive Scheme implementation of this automorphism, which acts on S-expressions, i.e. list-structures:)
(define *A130375! (!APPLY-AFTER-FIRST-NIL *A074685!))
(define (!APPLY-AFTER-FIRST-NIL f!) (letrec ((g! (lambda (s) (cond ((pair? s) (if (pair? (car s)) (g! (cdr s)) (f! (cdr s))))) s))) g!))
CROSSREFS
Inverse: A130376. a(n) = A074685(A130370(n)) = A074685(A130371(A074686(n))) = A130369(A130371(A130370(n))).
Sequence in context: A060126 A216250 A154121 * A154122 A089850 A154450
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jun 05 2007
STATUS
approved