In the discrete branches of mathematics and the computer
sciences, it will only take some seconds before you're faced
with a set like {1,...,m}. Some people write $1\ldotp\ldotp m$,
others $\{j:1\leq j\leq m\}$, and the journal you're submitting
to might want something else entirely. The 12many package
provides an interface that makes changing from one to another a
one-line change.