number-theory / Number Theory, Unit Fractions

Erdős Problem #306

If $a/b \in \mathbb{Q}_{>0}$ and $b$ is squarefree, can $a/b$ always be written as a finite sum of reciprocals of distinct products of two distinct primes?

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number-theoryJun 19, 2026Significance 10/100Registry: lean verified

Erdős Problem #306

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If $a/b \in \mathbb{Q}_{>0}$ and $b$ is squarefree, can $a/b$ always be written as a finite sum of reciprocals of distinct products of two distinct primes?

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If $a/b \in \mathbb{Q}_{>0}$ and $b$ is squarefree, can $a/b$ always be written as a finite sum of reciprocals of distinct products of two distinct primes?

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Erdős Problem #306 — Mathematical Frontier Network