Half-arc-transitive graphs of order 4p of valency twice a prime
Half-arc-transitive graphs of order 4p of valency twice a prime
A graph is half-arc-transitive if its automorphism group acts transitively on vertices and edges, but not on arcs. Let p be a prime. Cheng and Oxley [On weakly symmetric graphs of order twice a prime, J. Combin. Theory B 42 (1987), 196−211] proved that there is no half-arc-transitive graph of …