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Problem #389: Is it true that for every $n\geq 1$ there is a $k$ such...

Is it true that for every $n\geq 1$ there is a $k$ such that\[n(n+1)\cdots(n+k-1)\mid (n+k)\cdots (n+2k-1)?\]

Problem Statement

Is it true that for every $n\geq 1$ there is a $k$ such that\[n(n+1)\cdots(n+k-1)\mid (n+k)\cdots (n+2k-1)?\]
Categories: Number Theory

Progress

Asked by Erdős and Straus.
For example when $n=2$ we have $k=5$:\[2\times 3 \times 4 \times 5\times 6 \mid 7 \times 8 \times 9\times 10\times 11.\]and when $n=3$ we have $k=4$:\[3\times 4\times 5\times 6 \mid 7\times 8\times 9\times 10.\]Bhavik Mehta has computed the minimal such $k$ for $1\leq n\leq 18$ (now available as A375071 on the OEIS).

Source: erdosproblems.com/389 | Last verified: January 14, 2026

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