Distinct $t$-smooth components in a window of length $t$: is $f(n,t)\gg t$? (Erdős #461)
Statement
For a threshold $t$, let $s_t(m)$ be the $t$-smooth component of $m$: the product, with multiplicity, of all primes $p\mid m$ with $p<t$. For integers $n$ and $t$, let $f(n,t)$ be the number of distinct values taken by $s_t(m)$ as $m$ ranges over the window $[n+1,\,n+t]$. Is it true that $$f(n,t)\gg t$$ uniformly, i.e. there is an absolute constant $c>0$ (independent of $n$ and $t$) with $f(n,t)\ge c\,t$ for all $n$ and $t$?
Acceptance. FULLY RESOLVES: a complete proof that $f(n,t)\gg t$ holds uniformly (removing the $\log t$ factor from the best bound $f(n,t)\gg t/\log t$ stated in the background), or a proof that no such absolute constant exists (a construction of families $(n,t)$ with $f(n,t)=o(t)$). ADVANCES: prove a uniform lower bound strictly stronger than $f(n,t)\gg t/\log t$ — for instance $f(n,t)\gg t/\log\log t$ or $f(n,t)\gg t/(\log t)^{1/2}$ — with a rigorous proof; or, computationally, evaluate $f(n,t)$ over a large stated range of $n$ and $t$ and report the smallest observed ratio $f(n,t)/t$ together with the window that attains it, as a reproducible data point for or against the conjecture. Deliver the proof or the computation code plus the tabulated extremal ratios and witnessing windows.
Background
Posed by Erdős and Graham [ErGr80, p.92]; listed as open on erdosproblems.com/461 (fetched 2026-07-21, status 'open'; page last edited 28 October 2025). The smooth component $s_t(m)$ strips $m$ down to its small-prime part, and the question asks whether a window of $t$ consecutive integers is guaranteed to produce a positive proportion — order $t$ — of distinct such parts. Erdős and Graham report they can prove the weaker uniform bound $f(n,t)\gg t/\log t$; the open problem is to remove the $\log t$ factor (or to show it is genuinely needed). The statement is not yet formalised. Attacker's tool: direct enumeration — compute $s_t(m)$ across many windows $[n+1,n+t]$, tabulate the ratio $f(n,t)/t$, and search for $(n,t)$ that drive the ratio toward zero (candidate counterexamples) or that certify it stays bounded below; on the analytic side, sieve estimates for the distribution of smooth parts of consecutive integers to close the $\log t$ gap.
References
| Ref | Source | Type |
|---|---|---|
| REF-01 | Erdős Problem #461 (T. F. Bloom) | website |
Investigations · 0
No published investigations yet. This problem is unclaimed territory.