
In this paper, we deal with recursive constructions for incomplete group divisible designs (IGDDs). Denoting
We investigate the labellings of sum graphs, necessary conditions for a graph to be a sum graph, and the range of edge numbers of sum graphs.
A set
We derive a first-order recurrence for
Avis has shown that the number of vertices of a minimal triangle-free
By a refinement of a rank argument used to prove a directed version of the Graham-Pollak theorem, we show that
In this paper, we obtain a polynomial inequality of degree three in
Let
Let
For each integer
If
Let
The Josephus problem is concerned with anticipating which will be the last elements left in the ordered set
In a secret sharing scheme, a dealer has a secret. The dealer gives each participant in the scheme a share of the secret. There is a set
It is shown that the collection of all
The set of Lyndon words of length
The conjugation relation among the subspaces of a finite unitary geometry and its properties are studied. Then they are used to find some enumeration formulas for the subspaces of the unitary geometry, to prove a type of transitivity of the unitary group, to construct Partially Balanced Incomplete Block (PBIB) designs, and to establish the isomorphism between some known PBIB designs.
Incomplete group divisible designs (IGDDs) are the group divisible designs (GDDs) missing disjoint sub-GDDs, which need not exist. We denote by
The
For positive integers
1970-2025 CP (Manitoba, Canada) unless otherwise stated.