オイラー積
The product structure also explains the classical Euler product for the zeta function. The zeta function of "D" corresponds to a Cartesian product of zeta functions of the factors, computed above as formula_59 so that formula_60 where the right side is a Cartesian product. Applying the isomorphism which sends "t" in the "k"th factor to formula_61, we obtain the usual Euler product.