4-blocked hadamard 3-designs Original Research Article

The important role of Hadamard designs for applications in several fields has been long established. A considerable problem of finite geometry is to determine the configurations of the minimum number of points that block a design, i.e. the shape of a minimum set of points which have at least one point in common with any block. In this paper we deal with Hadamard 3-designs blocked by only four points.