How to properly represent natural numbers less than n?

Question

What is the better representation for natural numbers $x$ less equal a number $n>0$ in a scientific paper?

1. $x \in \textbf{N}_{\le n}$ or
2. $x \in \{1, \ldots, n\}$ or
3. $0 \lt x \le n$?

Answer 1

I've never seen the first one, but I'm sure someone has used it. The other two are definitely used. Conventions vary from one field to the next. The kind I would personally use is:

$$x\in[n].$$