Let $z$ be a complex number, $a$ a real number. Define $x_n=(a\cdot z)^n$. Find an expression for $|x_n|$ for all $n \in \mathbb{N}$.
How should I understand this question? I already got the polarform of $z$. Should that be used here. The notation of finding the modulus of a sequence for all $n \in \mathbb{N}$ is throwing me off. What does this mean?