In this paper consideration is
given semigroups which arise from a group (G,⋅) by defining a binary operation ∘ on
G by the rule x∘y = xϕyψ for all x,y in G, where ϕ,ψ are endomorphisms of G. In
particular, the structure of such semigroups is determined. Also determined are the
structure and number of semigroups that can be defined by x∘y = axsyt for all x,y
in G, where (G,⋅) is a finite abelian group containing a, and s,t are nonnegative
integers.
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