Possible Duplicate:
when is A isomorphic to A^3?
Does there exist a group $G$ such that $G \cong G \times G \times G$ and $G \not \cong G \times G$? If such groups exist, can $G$ be countable?
Tangentially, it is known that there is no such linear order (replacing direct product with concatenation) and that there are such Boolean algebras (replacing direct product with direct sum).