DM
1998
13 years 11 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 11 months ago
1998
DM
1998
13 years 11 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 11 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 11 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 11 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 11 months ago
1998
DM
1998
13 years 11 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 11 months ago
1998
DM
1998
13 years 11 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...