On semigroups admitting ring structure II

We shall consider semigroups with O, which contain a unique maximal right ideal generated by a finite number of independent generators and in which every proper right ideal is contained in the unique maximal right ideal and investigate when these semigroups are multiplicative semigroups of a ring. We prove in particular that the necessary condition for this class of semigroups S to admit ring structure is S=S² if |S|>2. Furthermore the admissible ring structure of S is determined when the product of every two generators of the maximal right ideal M is O and when S satisfies one of the two conditions, namely S is commutative without idempotents except O and 1 or every generator of M is nilpotent.