# Ihara zeta function

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Let $X$ be a finite graph. The Ihara zeta function is given by the formula $$\zeta_X(t) = \displaystyle\prod_{[C]} \dfrac{1}{1-t^{|C|}},$$ where $[C]$ is the set of equivalence classes of primitive closed paths $C$ in $X$ and $|C|$ denotes the length of $C$. This formula is an analogue of the Euler product representation of the Riemann zeta function.