The Fine Structure of \((v, 3)\) Directed Triple Systems: \(v \equiv 2 \pmod{3}\)

Peter Adams1, Darryn E. Bryant1, A. Khodkar1
1Centre for Discrete Mathematics and Computing Department of Mathematics The University of Queensland 4072, Australia

Abstract

The fine structure of a directed triple system of index \(\lambda\) is the vector \((c_1,c_2,\ldots,c_\lambda)\), where \(c_i\) is the number of directed triples appearing precisely \(i\) times in the system. We determine necessary and sufficient conditions for a vector to be the fine structure of a directed triple system of index \(3\) for \(v \equiv 2 \pmod{3}\).