Enumerative combinatorics
Constructive combinatorics
Chords, trees, and permutations
Discrete Mathematics
A classic proof of a recurrence for a very classical sequence
Journal of Combinatorial Theory Series A
Enumeration of noncrossing trees on a circle
Proceedings of the 7th conference on Formal power series and algebraic combinatorics
Analytic combinatorics of non-crossing configurations
Discrete Mathematics - Special issue on selected papers in honor of Henry W. Gould
Noncrossing trees are almost conditioned Galton--Watson trees
Random Structures & Algorithms
Dyck paths with coloured ascents
European Journal of Combinatorics
Bijections for 2-plane trees and ternary trees
European Journal of Combinatorics
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The number Nn of non-crossing trees of size n satisfies Nn+1 = Tn, where Tn enumerates ternary trees of size n. We constuct a new bijection to establish that fact. Since Tn = (1/(2n + 1))(3nn), it follows that 3(3n - 1)(3n - 2)Tn-1 =2n(2n + 1)Tn. We construct two bijections "explaining" this recursion; one of them easily extends to the case of t-ary trees.