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Abstract

Consider the power series $\mathfrak{A}(z)= \sum_{n=1}^{\infty}\alpha(n)z^n$, where $\alpha(n)$ is an additive function satisfying the condition $\alpha(p^m)=mf(p,m)\ln p$, where $f(p,m)\to 0$ as $p\to \infty$ uniformly with respect to $m$. Denote by $e(l/q)$ the root of unity $e^{2\pi il/q}$. For such series we give effective omega-estimates for $\mathfrak{A}(e(l/p^k)r)$ as $r\to 1-$. From the estimates we deduce that if such a series has non-singular points on the unit circle then it is a rational function.