number-theory / Number theory

Erdos's Question on Shifted Pairwise-Coprime Reciprocal Sums

Let $\mathcal{M}(n)$ be the supremum of $\sum_{a \in A} 1/(n-a)$ over pairwise coprime $A \subset [1,n)$. Erdos asked whether $\mathcal{M}(n) \le \sum_{p<n} 1/p + O(1)$ uniformly. The average order is settled: $\sum_{n \le N} \mathcal{M}(n) = e^{-\gamma} N \log\log N + O(N)$.

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Let $\mathcal{M}(n)$ be the supremum of $\sum_{a \in A} 1/(n-a)$ over pairwise coprime $A \subset [1,n)$. Erdos asked whether $\mathcal{M}(n) \le \sum_{p<n} 1/p + O(1)$ uniformly. The average order is settled: $\sum_{n \le N} \mathcal{M}(n) = e^{-\gamma} N \log\log N + O(N)$.

the average order; the uniform bound Erdos asked about is not settled

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Erdos's Question on Shifted Pairwise-Coprime Reciprocal Sums — Mathematical Frontier Network