5-Designs with three intersection numbers

t-Designs with few intersection numbers

Pott, A. and M. Shriklande, t-Designs with few intersection numbers, Discrete Mathematics 90 (1991) 215-217. We give a method to obtain new i-designs from t-designs with j distinct intersection numbers if i + j 1 does not exceed t.

Block Intersection Numbers of Block Designs Ii

A Note on t-designs with t Intersection Numbers

Let X be a finite set of v elements, called points, and let β be a finite family of distinct k-subsets of X , called blocks. Then the pair D = (X ,β) is called a t-design with parameters (v,k,λ) if any t-subset of X is contained in exactly λ members of β. If λi denotes the number of blocks containing i points, i = 0,1,2, . . . , t−1, then λi is independent of the choice of the i points and λi (...

On quasi-symmetric designs with intersection difference three

In a recent paper, Pawale [22] investigated quasi-symmetric 2-(v, k, λ) designs with intersection numbers x > 0 and y = x+ 2 with λ > 1 and showed that under these conditions either λ = x + 1 or λ = x + 2, or D is a design with parameters given in the form of an explicit table, or the complement of one of these designs. In this paper, quasi-symmetric designs with y−x = 3 are investigated. It is...

Symmetric Designs, Sets with Two Intersection Numbers and Krein Parameters of Incidence Graphs

Let (P; B;I) be a symmetric (v; k;) block design. The incidence graph G of this design is distance-regular, hence belongs to an association scheme. In this paper, we use the algebraic structure of this association scheme to analyse certain symmetric partitions of the incidence structure. A set with two intersection numbers is a subset P1 P with the property that jB \P1j takes on only two values...