For a partition Formula: see text of a set Formula: see text, we say that a transformation Formula: see text of Formula: see text preserves Formula: see text if for every Formula: see text there exists Formula: see text such that Formula: see text. Let Formula: see text denote the semigroup of all transformations Formula: see text of Formula: see text such that Formula: see text preserves Formula: see text and its image Formula: see text intersects each block of Formula: see text. We describe Green's relations on Formula: see text and prove that Green's relations Formula: see text and Formula: see text on Formula: see text are equal if and only if Formula: see text is finite. Moreover, we characterize ideals and the kernel of Formula: see text and determine when the semigroup Formula: see text is unit-regular, orthodox, inverse, and completely regular separately.
Sarkar et al. (Thu,) studied this question.
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