EN
Let $d_{α,β}(n) = ∑ _{n=kl, αl<k≤βl} 1$ be the number of ways of factoring n into two almost equal integers. For fixed rational numbers α > 0 and β > 0, we consider a zeta function of the type $ζ_{α,β}(s) = ∑_{n=1}^{∞} d_{α,β}(n)/n^{s}$ for ℜs > 1. It has an analytic continuation to ℜs > 1/3. We get an asymptotic formula for the mean square of $ζ_{α,β}(s)$ in the strip 1/2 < ℜs < 1. As an application, we improve a result on the distribution of primitive Pythagorean triangles.