On Number of Idempotent Elements in Finite Semigroup of Full Order -Preserving Contractions

In this paper, we considered the semigroupOCTn consisting of all mappings of a-finite set Xn - (1, 2, 3, - - - , n} which are both order — preserving and contraction, that is mappinga : Xn -» Xn ^ ich that, for all ,y e Xn, x => x a £ y a,anc | x a — *y a <1 x—y| . In particular, we proposed a closed form formula for the number of idempotent elements in OCTn, (that is elements oc satisfying oc2=oc).