Hopf-Galois structures of squarefree degree.

Let n be a squarefree natural number, and let G , Γ be two groups of order n. We determine the number of Hopf-Galois structures of type G admitted by a Galois extension of fields with Galois group isomorphic to Γ. We give some examples, including a full treatment of the case where n is the product of three primes. [ABSTRACT FROM AUTHOR]