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97
Voted
DM
1998
15 years 13 days ago
1998
We introduce three deÿnitions of q-analogs of Motzkin numbers and illustrate some combinatorial interpretations of these q-numbers. We relate the ÿrst class of q-numbers to the ...
91
Voted
DM
1998
15 years 13 days ago
1998
Cameron introduced a natural probability measure on the set S of sum-free sets, and asked which sets of sum-free sets have a positive probability of occurring in this probability m...
DM
1998
15 years 13 days ago
1998
Let β(G), Γ(G) and IR(G) be the independence number, the upper domination number and the upper irredundance number, respectively. A graph G is called Γperfect if β(H) = Γ(H),...
103
Voted
DM
1999
15 years 12 days ago
1999
We characterize bipartite Steinhaus graphs in three ways by partitioning them into four classes and we describe the color sets for each of these classes. An interesting recursion ...
73
Voted
DM
2006
15 years 23 days ago
2006
The group PSL(2, q) is 3-homogeneous on the projective line when q is a prime power congruent to 3 modulo 4 and therefore it can be used to construct 3-designs. In this paper, we ...