DM
1998
13 years 9 months 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 ...
DM
1998
13 years 9 months ago
1998
DM
1998
13 years 9 months ago
1998
We consider edge-coloured multigraphs. A trail in such a multigraph is alternating if its successive edges differ in colour. Let G be a 2-edge-coloured complete graph and let M b...
DM
1998
13 years 9 months ago
1998
A basis of the cycle space C(G) of a graph G is h-fold if each edge of G occurs in at most h cycles of the basis. The basis number b(G) of G is the least integer h such that C(G) ...
DM
1998
13 years 9 months ago
1998
We give a counterexample to a conjecture by Wild about binary matroids. We connect two equivalent lines of research in matroid theory: a simple type of basis-exchange property and ...
DM
1998
13 years 9 months ago
1998
Let G be a median graph on n vertices and m edges and let k be the number of equivalence classes of the Djokovi´c’s relation Θ defined on the edge-set of G. Then 2n − m −...
DM
1998
13 years 9 months ago
1998
DM
1998
13 years 9 months ago
1998
An embedding of Kn into a hypercube is a mapping of the n vertices of Kn to distinct vertices of the hypercube, and the associated cost is the sum over all pairs of (mapped) verti...
DM
1998
13 years 9 months ago
1998
DM
1998
13 years 9 months ago
1998
One class of Davenport-Schinzel sequences consists of finite sequences over n symbols without immediate repetitions and without any subsequence of the type abab. We present a bij...