Erdős Problem a Daythe open tracker

Erdős Problem #430

OPENdatabase updated 2025-08-31

No proof or disproof is known, and it isn't known whether a finite computation could settle it.

What the community database records, not our verdict. erdosproblems.com no longer shows statuses (why).

The terms of the sequence of Erdős Problem 430 for a given \(n\): the integers \(m\) with \(1 < m < n\) all of whose prime factors are \(> n - m\). The decreasing sequence \(a_1 > a_2 > \cdots\) of the problem lists the elements of this set in decreasing order: \(a_1 = n - 1\) is its largest element and \(a_k\) is its largest element below \(a_{k-1}\). The integer \(1\) has no prime factors and is not a term of the sequence, which stops instead, as in the example on erdosproblems.com: for \(n = 8\) the sequence is

Fix some integer \(n\) and define a decreasing sequence in \([1,n)\) by \(a_1=n-1\) and, for \(k\geq 2\), letting \(a_k\) be the greatest integer in \([1,a_{k-1})\) such that all of the prime factors of \(a_k\) are \(>n-a_k\). Is it true that, for sufficiently large \(n\), not all of this sequence can be prime?
Statement as formalized in Formal Conjectures (Google DeepMind, Apache-2.0) · their label: research open. The authoritative wording is on erdosproblems.com/430.
Prizenone
Topicsnumber theory
Statement in LeanFormal Conjectures
Solution in Leanno
OEISA322293
Original pageerdosproblems.com/430
WORKING REPORT BY THIS SITE · JUL 28, 2026

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exactly 100 exceptions are certified for 5 <= n <= 10^10 (last 267680), with an elementary reduction and standalone checker; the uniform semiprime-gap step remains open.

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