The existence of three idempotent IMOLS Original Research Article

In this paper it is shown that an idempotent TD(5,m)−TD(5,n) exists whenever the known necessary condition m⩾4n+1 is satisfied, except when (m,n)=(6,1) and possible when (m,n)=(10,1). For m<60 and n⩽10, we also indicate where several idempotent TD(k,m)−TD(k,n)ʹs for k=6,7 can be found.