In elementary number theory, I find the following notations being used interchangeably, which leads me to have many ambiguous assumptions:
- $\mathbb{Z}_p^\times$;
- $\mathbb{Z}_p$,
where p is any integer. What's the difference between them?
One more question to add to the kitty: what do they mean when they say "a subgroup of $\mathbb{Z}_p$, where p is prime"?
It will be nice if someone can enlighten me on this elementary notation.
Thanks.