Symmetric (not Complete Intersection) Semigroups Generated by Five Elements

Abstract

We consider symmetric (not complete intersection) numerical semigroups S_5, generated by five elements, and derive inequalities for degrees of syzygies of S_5 and find the lower bound F_5 for their Frobenius numbers. We study a special case W_5 of such semigroups, which satisfy the Watanabe Lemma, and show that the lower bound F_{5w} for the Frobenius number of the semigroup W_5 is stronger than F_5.