The directed packing numbers DD(t, v ,v), t ≥ 4

A directed packing is a maximal collection of k-subsets, called blocks, of a set of cardinality v having the property that no ordered t-subset occurs in more than one block. A block contains an ordered t-set if its symbols appear, left to right, in the block. The cardinality of such a maximal collection is denoted by DD(t, k, v). We consider the special case when k=v and derive some results on the sizes of maximal collections.