PROVED
This has been solved in the affirmative.
- $250
The density of integers which have two divisors $d_1,d_2$ such that $d_1<d_2<2d_1$ exists and is equal to $1$.
In
[Er79] asks the stronger version with $2$ replaced by any constant $c>1$.
The answer is yes (also to this stronger version), proved by Maier and Tenenbaum
[MaTe84]. (Tenenbaum has told me that they received \$650 for their solution.)
In
[Er64h] claimed a proof that the set of integers $n$ with divisors\[d_1<d_2<d_1(1+(\log n)^{-\beta})\]has density $1$ if $\beta<\log 3-1$, but this claim was retracted in
[ErHa79]. Erdős and Hall
[ErHa79] proved that this set has density $0$ if $\beta >\log 3-1$ (in a stronger quantitative form). The proof of Maier and Tenenbaum
[MaTe84] proves that the density is $1$ if $\beta<\log 3-1$.
This is discussed in problem E3 of Guy's collection
[Gu04].
See also
[449] and
[884].
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This page was last edited 29 December 2025.
Additional thanks to: Wouter van Doorn
When referring to this problem, please use the original sources of Erdős. If you wish to acknowledge this website, the recommended citation format is:
T. F. Bloom, Erdős Problem #144, https://www.erdosproblems.com/144, accessed 2026-01-16