Problem of the Week
BUGCAT
Zassenhaus Conference
Hilton Memorial Lecture
BingAWM
Math Club
Actuarial Association
A semigroup is a set with an associative operation. A subsemigroup is a subset which is a semigroup with the same operation. σ(S), the covering number of a semigroup S (with respect to subsemigroups), is the minimum number of proper subsemigroups whose union is S. I will give a complete description of the covering numbers of finite semigroups.