

A080981


A014486encodings of the trees whose interior zigzagtree (Stanley's c) is branchreduced (in the sense defined by Donaghey).


5



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
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OFFSET

0,2


COMMENTS

Donaghey defines (on page 82 of his paper) the branchreduced zigzagtrees as those zigzagtrees which do not contain longer than oneedge 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.


REFERENCES

R. Donaghey, Automorphisms on Catalan trees and bracketing, J. Combin. Theory, Series B, 29 (1980), 7590.


LINKS

Table of n, a(n) for n=0..48.
A. Karttunen, Initial terms illustrated in positions 0, 1, 2, 3, 5, 6, 7, 11, 12, 15, 16, 18, 20, 29, 30, 32, ...


CROSSREFS

a(n) = A014486(A080980(n)). Cf. A080968, A080971. These trees are enumerated by A005554.
Sequence in context: A144145 A075170 A039571 * A106455 A209445 A181427
Adjacent sequences: A080978 A080979 A080980 * A080982 A080983 A080984


KEYWORD

nonn


AUTHOR

Antti Karttunen Mar 02 2003


STATUS

approved



