Erdős Problem a Daythe open tracker

Erdős Problem #393

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).

`f n` is \(f(n)\), the minimal \(m \geq 1\) such that \(n! = a_1 \cdots a_t\) with \(a_1 < \cdots < a_t = a_1 + m\). The factors are recorded as a finite set \(s \subseteq [a, a + m]\) of natural numbers that contains \(a = a_1\) and \(a + m = a_t\). Since \(m \geq 1\) there are at least two factors, and they are positive because \(n! \neq 0\). Such a factorisation exists for \(n \geq 2\). For \(n \leq 1\) there is none, since \(n! = 1\), and `f n` is the junk value `0`.

Let \(f(n)\) denote the minimal \(m\geq 1\) such that \[n! = a_1\cdots a_t\] with \(a_1<\cdots <a_t=a_1+m\). What is the behaviour of \(f(n)\)? We formalise the question as: does \(f(n) \to \infty\)? A result of Luca [Lu02] implies a positive answer, conditional on the \(abc\) conjecture (see `Erdos393.erdos_393.variants.luca`).
Statement as formalized in Formal Conjectures (Google DeepMind, Apache-2.0) · their label: research open · 4 further variants / known partial results in the Lean file. The authoritative wording is on erdosproblems.com/393.
Prizenone
Topicsnumber theory, factorials
Statement in LeanFormal Conjectures
Solution in Leanno
OEISA388302
Original pageerdosproblems.com/393
WORKING REPORT BY THIS SITE · JUL 28, 2026

Read our working report →

Exact exhaustive computation extends A388302 from n=79 through n=100 (in particular f(80)=76), with a complete geometric-mean reduction and standalone verifier; the uniform asymptotic problem remains

PARTIAL