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 A069770 Signature permutation of the first non-identity, nonrecursive Catalan automorphism in table A089840: swap the top-branches of a binary tree. An involution of nonnegative integers. 92
 0, 1, 3, 2, 7, 8, 6, 4, 5, 17, 18, 20, 21, 22, 16, 19, 14, 9, 10, 15, 11, 12, 13, 45, 46, 48, 49, 50, 54, 55, 57, 58, 59, 61, 62, 63, 64, 44, 47, 53, 56, 60, 42, 51, 37, 23, 24, 38, 25, 26, 27, 43, 52, 39, 28, 29, 40, 30, 31, 32, 41, 33, 34, 35, 36, 129, 130, 132, 133, 134 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS This is the simplest possible Catalan automorphism after the identity automorphism *A001477. It effects the following transformation on the unlabeled rooted plane binary trees (letters A and B refer to arbitrary subtrees located on those nodes): .A...B....-->....B...A. ..\./.............\./.. ...x...............x... (a . b) ------> (b . a) REFERENCES A. Karttunen, paper in preparation, draft available by e-mail. LINKS A. Karttunen, Table of n, a(n) for n = 0..2055 EXAMPLE To obtain the signature permutation, we apply these transformations to the binary trees as encoded and ordered by A014486 and for each n, a(n) will be the position of the tree to which the n-th tree is transformed to, as follows: ...................one tree of one internal. ..empty tree.........(non-leaf) node........ ............................................ ......x......................\/............. n=....0......................1.............. a(n)=.0......................1.............. (both are always fixed) the next 7 trees, with 2-3 internal nodes, in range [A014137(1), A014138(2)] = [2,8] change as follows: ..........................\/.....\/.................\/.....\/... .......\/.....\/.........\/.......\/.....\/.\/.....\/.......\/.. ......\/.......\/.......\/.......\/.......\_/.......\/.......\/. n=.....2........3........4........5........6........7........8.. ..............................|................................. ..............................|................................. ..............................V................................. ................................................................ ........................\/.....\/.....................\/.....\/. .....\/.........\/.....\/... ...\/.......\/.\/.......\/.......\/ ......\/.......\/.......\/.......\/.......\_/.......\/.......\/. a(n)=..3........2........7........8........6........4........5.. thus we obtain the first nine terms of this sequence: 0, 1, 3, 2, 7, 8, 6, 4, 5. PROG (Scheme implementations of this automorphism. These act on S-expressions, i.e. list-structures:) (CONSTRUCTIVE VERSION:) (define (*A069770 s) (if (pair? s) (cons (cdr s) (car s)) s)) (DESTRUCTIVE VERSION:) (define (*A069770! s) (if (pair? s) (let ((ex-car (car s))) (set-car! s (cdr s)) (set-cdr! s ex-car))) s) CROSSREFS Row 1 of A089840. a(n) = A083927(A072796(A057123(n))) = A083927(A057508(A057123(n))) = A083927(A057509(A057123(n))). The number of cycles (A007595) and the number of fixed points (A000108 interleaved with zeros) in range [A014137(n-1)..A014138(n-1)] of this permutation are given by the same sequences as for the following recursive derivations of this automorphism: *A057163 and *A122351. Other related sequences: A069767, A069768, A089864, A123492. Sequence in context: A130959 A130928 A154126 * A129612 A154455 A082345 Adjacent sequences:  A069767 A069768 A069769 * A069771 A069772 A069773 KEYWORD nonn AUTHOR Antti Karttunen, Apr 16 2002. Entry revised Oct 11 2006. STATUS approved

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Last modified October 17 15:30 EDT 2019. Contains 328116 sequences. (Running on oeis4.)