The Narayana numbers n appear twice in Volume 31 of Discrete Mathematics: They count the ordere0 trees with n edges (i.e. n+l nodes) and k leaves [1] and the noncrossing partitions of {1 ..... n} into k blocks . (In such a partition the existence of four numbers a<b<c<d such that a and c are in one
On trees and noncrossing partitions
โ Scribed by Martin Klazar
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 426 KB
- Volume
- 82
- Category
- Article
- ISSN
- 0166-218X
No coin nor oath required. For personal study only.
โฆ Synopsis
We give a simple and natural proof of (an extension of) the identity P(X. 1. )I ) = t-'2( X I. I -I. II --I ). The number P(li, I, 17) counts noncrossing partitions of { I, 2.
I} unto II parts such that no part contains two numbers .Y and J'. O<.v --.v<k. The lower index 2 indicate\ partitions with no part of size three or more. We USC the identity to give quick proofs of the closed t'ormulac for P(k. I, n) when k is I. 2. or 3.
๐ SIMILAR VOLUMES
Simion, R. and D. Ullman, On the structure of the lattice of noncrossing partitions, Discrete Mathematics 98 (1991) 193-206. We show that the lattice of noncrossing (set) partitions is self-dual and that it admits a symmetric chain decomposition. The self-duality is proved via an order-reversing i
The partitions of a natural number n (with parts taken in non-increasing order), may be listed in dictionary order. This ordering of partitions is shown to correspond to the post ordering of chains of a finite tree T[n]. It is shown that T[n] belongs to a, the class of normal trees. % occurs indepen
We crgnsider the minimum m\*-nber T(G) of subsets intl:, which the edge set E(G) of a graph G can lx partitioned so that each subset forms a tree. It is shown that for any connected (3 with II vertices, we always have T( Gj s [$I.
We present observations and problems connected with a weighted binary tree representation of integer partitions. ๏ฃฉ 2002 Elsevier Science (USA)
Bijections are presented between certain classes of trees and multichains in non-crossing partition lattice'+.