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Search: id:A080981
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| A080981 |
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A014486-encodings of the trees whose interior zigzag-tree (Stanley's c) is branch-reduced (in the sense defined by Donaghey). |
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5
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| 0, 2, 10, 12, 44, 50, 52, 178, 180, 204, 210, 216, 228, 716, 722, 728, 740, 818, 820, 844, 866, 868, 872, 914, 920, 932, 2866, 2868, 2892, 2914, 2916, 2920, 2962, 2968, 2980, 3276, 3282, 3288, 3300, 3378, 3380, 3468, 3474, 3480, 3490, 3492, 3504, 3528, 3660
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Donaghey defines (on page 82 of his paper) the branch-reduced zigzag-trees as those zigzag-trees which do not contain longer than one-edge branches, where a branch is a maximal connected set of edges slanted to the same direction, with no perpendicular edges emanating from its middle. These form the primitive elements of the automorphism A057505/A057506.
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REFERENCES
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R. Donaghey, Automorphisms on Catalan trees and bracketing, J. Combin. Theory, Series B, 29 (1980), 75-90.
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LINKS
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A. Karttunen, Initial terms illustrated in positions 0, 1, 2, 3, 5, 6, 7, 11, 12, 15, 16, 18, 20, 29, 30, 32, ...
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CROSSREFS
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a(n) = A014486(A080980(n)). Cf. A080968, A080971. These trees are enumerated by A005554.
Sequence in context: A144145 A075170 A039571 this_sequence A106455 A055697 A055705
Adjacent sequences: A080978 A080979 A080980 this_sequence A080982 A080983 A080984
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KEYWORD
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nonn
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AUTHOR
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Antti Karttunen (my_firstname.my_surname(AT)iki.fi) Mar 02 2003
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