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Erdős problem 1061

Let S(x)S(x) count ordered pairs (a,b)(a,b) with a+b≤xa+b \le x and σ(a)+σ(b)=σ(a+b)\sigma(a)+\sigma(b) = \sigma(a+b). Erdos asked whether S(x)∼cxS(x) \sim cx. The opposite extreme holds: for every R>0R > 0, S(x)/(x(log⁡x)R)→∞S(x)/(x(\log x)^R) \to \infty, so the count beats every fixed logarithmic scale.

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Let $S(x)$ count ordered pairs $(a,b)$ with $a+b \le x$ and $\sigma(a)+\sigma(b) = \sigma(a+b)$. Erdos asked whether $S(x) \sim cx$. The opposite extreme holds: for every $R > 0$, $S(x)/(x(\log x)^R) \to \infty$, so the count beats every fixed logarithmic scale.

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