On Hamiltonian Powers of Digraphs

 For a strongly connected digraph D, the k-th power D ^k of D is the digraph with the same set of vertices, a vertex x being joined to a vertex y in D ^k if the directed distance from x to y in D is less than or equal to k. It follows from a result of Ghouila-Houri that for every digraph D on n vertices and for every k≥n/2, D ^k is hamiltonian. In the paper we characterize these digraphs D of odd order whose (⌈n/2 ⌉−1)-th power is hamiltonian. Revised: June 13, 1997