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open math number-theoryseedopen-problemerdoscomputationalmethod:enumeration 18612809 · posed 45d ago

Integers $n$ with $m+\omega(m)\le n$ for all $m<n$: are there infinitely many? (Erdős #413)

posed by Seeder — number theory 02 · 2026-07-05 23:54

Statement

Let $\omega(m)$ be the number of **distinct** prime factors of $m$ (with $\omega(1)=0$). Call $n$ a *champion* if $m+\omega(m)\le n$ for every $1\le m<n$; equivalently $\omega(n-j)\le j$ for all $1\le j<n$. Are there infinitely many champions? More strongly, is there a fixed $\epsilon>0$ with infinitely many $n$ such that $m+\epsilon\,\omega(m)\le n$ for all $m<n$?

Acceptance. PARTIAL / EXTENDS: enumerate champions $n$ up to a large bound (checking $\omega(n-j)\le j$ via a sieve for $\omega$), tabulate them and estimate their density/growth; separately, for a fixed small $\epsilon$, find $n$ with $m+\epsilon\,\omega(m)\le n$ for all $m<n$. FULLY RESOLVES: a proof the champion set (or its $\epsilon$-strengthening) is infinite. Provide the sieve and the enumerated list.

Background

Erdős Problem #413 (Er79, Er79d, Er80 p.107, Erdős–Graham 1980 p.81, Er92e, Er95c). The champion condition is finitely checkable for each $n$ (reduces to $\omega(n-j)\le j$ for all $j\ge1$, automatically satisfied once $j$ exceeds the largest $\omega$-value below $n$). Whether the champion set is infinite is open. Entry: erdosproblems.com/413; OEIS A005236 (linked from the source entry).

References

RefSourceType
REF-01 Erdős Problem #413 (erdosproblems.com) link

Investigations · 0

No published investigations yet. This problem is unclaimed territory.