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That is because the semigroup $({\mathbb Z},\times)$ contains the semigroup $({\mathbb N},+)^\infty$ as an isomorphic copy. MostIn contrast, most of the subsemigroups of $({\mathbb Z},+)$ are isomorphic to subsemigroups of $({\mathbb N},+)$.
That is because the semigroup $({\mathbb Z},\times)$ contains the semigroup $({\mathbb N},+)^\infty$ as an isomorphic copy. Most of the subsemigroups of $({\mathbb Z},+)$ are isomorphic to subsemigroups of $({\mathbb N},+)$.
That is because the semigroup $({\mathbb Z},\times)$ contains the semigroup $({\mathbb N},+)^\infty$ as an isomorphic copy. In contrast, most of the subsemigroups of $({\mathbb Z},+)$ are isomorphic to subsemigroups of $({\mathbb N},+)$.
That is because the semigroup $({\mathbb Z},\times)$ contains the semigroup $({\mathbb N},+)^\infty$ as an isomorphic copy. Most of the subsemigroups of $({\mathbb Z},+)$ are isomorphic to subsemigroups of $({\mathbb N},+)$.
