All Admissible \(3-(v, 4, \lambda)\) Directed Designs Exist

Mike Grannell1, Terry S.Griggs1, Kathleen A.S.Quinn1
1 Department of Pure Mathematics, The Open University, Walton Hall, Milton Keynes MK7 6AA

Abstract

In a \(t-(v,k,\lambda)\) directed design, the blocks are ordered \(k\)-tuples and every ordered \(t\)-tuple of distinct points occurs in exactly \(\lambda\) blocks (as a subsequence). We show that a simple \(3-(v,4,2)\) directed design exists for all \(v\). This completes the proof that the necessary condition \(\lambda v\equiv 0 \pmod 2\) for the existence of a \(3-(v,4,\lambda)\) directed design is sufficient.