Please reason step by step, and put your final answer within \boxed{}.
Given a sequence $\{a_n\}$ that satisfies: $a_1=1$, $a_2=2$, and $a_n = \frac{a_{n-1}}{a_{n-2}}$ for $n \geq 3 $ and $n \in N^*$, find the value of $a_{2017}$.
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