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EJC
2007
13 years 9 months ago
2007
We prove a conjecture of F. Chapoton relating certain enumerative invariants of (a) the cluster complex associated by S. Fomin and A. Zelevinsky with a finite root system and (b)...
EJC
2006
13 years 11 months ago
2006
With development of knowledge bases (KB) there appeared expert systems that use KBs to support them in decision making process. Decision Support Systems, that are the subject of th...
EJC
2006
13 years 9 months ago
2006
A tube (resp. an oval tube) in PG(3, q) is a pair T = {L, L}, where {L} L is a collection of mutually disjoint lines of PG(3, q) such that for each plane of PG(3, q) containing L...
EJC
2006
13 years 9 months ago
2006
1 The Ramsey number R(G1, G2) is the smallest integer p such that for any graph G on p vertices2 either G contains G1 or G contains G2, where G denotes the complement of G. In this...
EJC
2006
13 years 9 months ago
2006
Abstract. A leaf of a plane tree is called an old leaf if it is the leftmost child of its parent, and it is called a young leaf otherwise. In this paper we enumerate plane trees wi...