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A154454
Signature permutation of a Catalan bijection: The inverse of A154453.
6
0, 1, 2, 3, 4, 5, 6, 8, 7, 9, 10, 11, 12, 13, 14, 15, 19, 21, 22, 16, 20, 17, 18, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 51, 52, 56, 58, 59, 60, 62, 64, 63, 42, 43, 53, 57, 61, 44, 54, 45, 46, 47, 55, 48, 49, 50, 65, 66, 67, 68, 69, 70, 71
OFFSET
0,3
COMMENTS
This automorphism of rooted plane binary trees switches the two descendant trees for every other vertex as it descends along the 000... ray, but not starting swapping until at the left-hand side child of the root, leaving the root itself fixed. Specifically, *A154454 = psi(A154444), where the isomorphism psi is given in A153141 (see further comments there).
PROG
(Scheme function, destructive implementation of this automorphism acting on S-expressions:) (define (*A154454! s) (if (pair? s) (*A154456! (car s))) s)
CROSSREFS
Inverse: A154453. a(n) = A069768(A154452(n)) = A057163(A154450(A057163(n))). Cf. A069770, A154456.
Differs from its inverse A154453 for the first time at n=49, where a(49)=64, while A154454(49)=63. Differs from A089854 for the first time at n=49, where a(49)=64, while A089854(49)=63. Differs from A131173 for the first time at n=26, where a(26)=26, while A131173(26)=27.
Sequence in context: A089866 A089854 A154453 * A131173 A073286 A122312
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 17 2009
STATUS
approved