Density $d_t$ of $n$ representing $t$ as a sum of distinct divisors: is $d_t\sim c_1(\log t)^{-c_2}$? (Erdős #859)
Statement
For an integer $t\geq 1$, let $d_t$ be the natural density of the set of integers $n\in\mathbb{N}$ for which $t$ can be represented as a sum of distinct divisors of $n$. (Erdős proved that this density exists for every $t$.) Do there exist constants $c_1,c_2>0$ such that $$d_t\sim\frac{c_1}{(\log t)^{c_2}}$$ as $t\to\infty$?
Acceptance. FULLY RESOLVES: prove or disprove the asymptotic $d_t\sim c_1/(\log t)^{c_2}$ — either exhibit constants $c_1,c_2>0$ and prove that $d_t(\log t)^{c_2}\to c_1$, or prove that no such pair exists (e.g. that $d_t(\log t)^{c}$ fails to converge to a positive limit for every $c>0$); machine-checkable (Lean/Coq) preferred, else a complete written proof. ADVANCES: (a) narrow the exponent gap — prove an upper bound $d_t<(\log t)^{-c_4'}$ with $c_4'$ strictly larger than, and/or a lower bound $d_t>(\log t)^{-c_3'}$ with $c_3'$ strictly smaller than, the best explicit exponents stated in the literature, with proof; (b) prove one-sided regular variation of $d_t$ — e.g. that $\log(1/d_t)/\log\log t$ converges to a limit (which would be the exponent $c_2$) — with proof; (c) reproducible high-range computation of $d_t$ that pins the empirical exponent $c_2$ to a certified numerical interval and tests the single-power hypothesis, with code and a convergence analysis. Deliver the proof file, or the computation code + certified estimates.
Background
Posed by Erdős [Er70]; listed as open on erdosproblems.com/859 (fetched 2026-07-21, status 'open', tagged 'number theory | divisors'). Erdős [Er70] proved that the density $d_t$ exists for every $t$ and established the two-sided bound $$\frac{1}{(\log t)^{c_3}}<d_t<\frac{1}{(\log t)^{c_4}}$$ for some constants $c_3,c_4>0$. The open question is whether $d_t$ obeys a single clean power-of-logarithm law — a genuine asymptotic governed by one exponent $c_2$ (necessarily $c_4\leq c_2\leq c_3$) — rather than merely being trapped between two different powers of $\log t$. A formalized statement exists in the DeepMind formal-conjectures repository (FormalConjectures/ErdosProblems/859.lean). The problem sits in Erdős's 'sums of distinct divisors' circle alongside practical numbers (Erdős #18, erdosproblems.com/18) and the divisor partial-sum sets of Erdős #468 (erdosproblems.com/468). No cash prize is attached. The attacker's tools: large-scale computation of $d_t$ — estimating, for many $t$, the density of $n\leq X$ whose divisors admit a subset summing to $t$ (subset-sum dynamic programming over the divisor multiset) — to fit the exponent and test the single-power law, paired with analytic work tightening $c_3$ and $c_4$ toward a common value.
References
| Ref | Source | Type |
|---|---|---|
| REF-01 | Erdős Problem #859 (T. F. Bloom) | website |
| REF-02 | Formalized statement of Erdős #859 (DeepMind formal-conjectures, Lean) | website |
Investigations · 0
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