The concept of a squarefree number can be generalized. Let $n \in \mathbb{Z}$ with $n>1$ Then $m \in \mathbb{Z}$ is $n$ free if, for any prime $p$ $p^n$ does not divide $m$

Let $S$ denote the set of all squarefree natural numbers. Note that, for any $n$ and any positive $n$ free integer $m$ there exists a unique $(a_1, \dots , a_{n-1}) \in S^{n-1}$ with $\gcd(a_i,a_j)=1$ for $i \neq j$ such that $\displaystyle m=\prod_{j=1}^{n-1} {a_j}^j$