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Erdős problem 448

Let τ(n)\tau(n) count the divisors of nn and τ+(n)\tau^+(n) count the number of kk such that nn has a divisor in [2k,2k+1)[2^k, 2^{k+1}). Is it true that, for all ϵ>0\epsilon > 0, τ+(n)<ϵτ(n) \tau^+(n) < \epsilon \cdot \tau(n) for almost all nn?

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8 retained statements2415f78e850a

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FormalConjectures/ErdosProblems/

448.lean

Retained formal statement5 of 8

A more precise result of Hall and Tenenbaum [HaTe88, §4.6]: the upper density of {n:τ+(n)<ϵτ(n)}\{n : \tau^+(n) < \epsilon \cdot \tau(n)\} is ϵlog(2/ϵ)\ll \epsilon \cdot \log(2/\epsilon) as ϵ0+\epsilon \to 0^+.

FormalConjectures/ErdosProblems/448.leanErdos448.erdos_448.variants.hall_tenenbaum_upper_bound2 linesExact file
(fun ε => {n | ↑(Erdos448.tauPlus n) < ε * ↑n.divisors.card}.upperDensity) =O[nhdsWithin 0 (Set.Ioi 0)] fun ε =>  ε * Real.log (2 / ε)
SolvedStatement only, no proof

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