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DM
2006
91views more  DM 2006»
14 years 9 months ago
Restricted Dumont permutations, Dyck paths, and noncrossing partitions
We complete the enumeration of Dumont permutations of the second kind avoiding a pattern of length 4 which is itself a Dumont permutation of the second kind. We also consider some ...
Alexander Burstein, Sergi Elizalde, Toufik Mansour
DM
2006
89views more  DM 2006»
14 years 9 months ago
On set systems with a threshold property
For n, k and t such that 1 < t < k < n, a set F of subsets of [n] has the (k, t)threshold property if every k-subset of [n] contains at least t sets from F and every (k -...
Zoltán Füredi, Robert H. Sloan, Ken Ta...
DM
2006
143views more  DM 2006»
14 years 9 months ago
Characterization of eccentric digraphs
The eccentric digraph ED(G) of a digraph G represents the binary relation, defined on the vertex set of G, of being `eccentric'; that is, there is an arc from u to v in ED(G)...
Joan Gimbert, Nacho López, Mirka Miller, Jo...
62
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DM
2006
73views more  DM 2006»
14 years 9 months ago
Composition of Post classes and normal forms of Boolean functions
The class composition C K of Boolean clones, being the set of composite functions f(g1, . . . , gn) with f C, g1, . . . , gn K, is investigated. This composition C K is either...
Miguel Couceiro, Stephan Foldes, Erkko Lehtonen
DM
2006
73views more  DM 2006»
14 years 9 months ago
Contributions to zero-sum problems
A prototype of zero-sum theorems, the well-known theorem of Erdos, Ginzburg and Ziv says that for any positive integer n, any sequence a1, a2, . . . , a2n-1 of 2n-1 integers has a...
Sukumar Das Adhikari, Yong-Gao Chen, John Friedlan...