Generating sets of finite singular transformation semigroups

J.M. Howie proved that , the semigroup of all singular mappings of {1,aEuro broken vertical bar,n} into itself, is generated by its idempotents of defect 1 (in J. London Math. Soc. 41, 707-716, 1966). He also proved that if na parts per thousand yen3 then a minimal generating set for contains n(n-1)/2 transformations of defect 1 (in Gomes and Howie, Math. Proc. Camb. Philos. Soc. 101. 395-403, 1987). In this paper we find necessary and sufficient conditions for any set for transformations of defect 1 in to be a (minimal) generating set for .