	Ihara zeta函数	加权Ihara zeta函数
图G	$Z_{G} (u) = \prod_{[C]} {(1 - u^{\| C \|})}^{- 1}$	$Z_{G} (w, u) = \prod_{[C]} {(1 - w (C) u^{\| C \|})}^{- 1}$
图G的正则覆盖	$Z {(G^{α}, u)}^{- 1} = \prod_{[C]} {(1 - u^{\| C \| k})}^{n / k}$	$Z_{G^{α}} {(\tilde{w}, u)}^{- 1} = \prod_{[C]} {(1 - w {(C)}^{k} u^{\| C \| k})}^{n / k}$
图G的非正则覆盖	$Z {(G^{ϕ}, u)}^{- 1} = \prod_{[C]} \prod_{j = 1}^{n} {(1 - u^{\| C \| j})}^{c_{j}}$	$Z_{G^{ϕ}} {(\tilde{w}, u)}^{- 1} = \prod_{[C]} \prod_{j = 1}^{n} {(1 - w {(C)}^{j} u^{\| C \| j})}^{c_{j}}$