On the \((v,5,\lambda)\)-family of Bhaskar Rao designs
A Bhaskar Rao design BRD\((v,b,r,k,\lambda)\) is a \(v \times b\) matrix with \(0, \pm 1\) entries such that any two distinct rows are orthogonal and the matrix of the absolute values is the incidence matrix of a BIBD\((v,b,r,k,\lambda)\). In the paper under review, the authors consider BRDs with \(k=5\) and prove that the necessary divisibility conditions turn out to be sufficient for \(\lambda=4\), \(10\) and \(20\) with a few (possible or definite) exceptions.
scientific article; zbMATH DE number 1802357
scientific article