P(Square-free)

$k$ is a random positive integer in $[1,n]$ . Let $p(n)$ the probability of $k$ being square-free.

What is $\displaystyle\lim_{n\to\infty} p(n)$ ?

Clarification: A positive integer $a$ is square-free if $\sqrt{a}$ is in the simplified radical form.

For example, $2,15,66$ are square-free, and $4,45,98$ are not.