Math and science::Algebra::Aluffi

Subgroups of cyclic groups

The following two propositions determine every subgroup of every cyclic group.

Let $G$ be a subgroup of $Z$ . Then [ $G = ?$ ] for some $d \geq 0$ .

Let $G$ be a subgroup of $Z / n Z$ for some $n \geq 0$ . Then [ $G = ?$ ] for some $d \geq 0$ with [what condition?].

Can you recall the proofs?

15.05.2023