Structure of the semigroup $OT_n$

Abstract

We study the structure of the semigroup $OT_n$, which is a unique (up to an isomorphism) $R$-section of the semigroup $T_n$. For this semigroup, we describe Green relations, determine regular and nilpotent elements, describe maximal nilpotent subsemigroups, and determine the unique irreducible system of generatrices and maximal subsemigroups.