2020
DOI: 10.1016/j.jnt.2019.11.006
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Almost primes and the Banks–Martin conjecture

Abstract: It has been known since Erdős that the sum of 1/(n log n) over numbers n with exactly k prime factors (with repetition) is bounded as k varies. We prove that as k tends to infinity, this sum tends to 1. Banks and Martin have conjectured that these sums decrease monotonically in k, and in earlier papers this has been shown to hold for k up to 3. However, we show that the conjecture is false in general, and in fact a global minimum occurs at k = 6.

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Cited by 12 publications
(22 citation statements)
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“…where I k,q represents the set of monic polynomials in F q [x] with k irreducible factors counted with multiplicity. Analogously to the observation of Lichtman [8], we find that the conjecture is false for q = 2, 3, and 4 by direct numerical computation in Section 6.3. However, in this section we will show that for each k, there exists q k such that the inequality holds up to F (I k,q ) for all q ≥ q k , and we will establish an upper bound on the size of q k .…”
Section: The Banks-martin Inequalitysupporting
confidence: 81%
“…where I k,q represents the set of monic polynomials in F q [x] with k irreducible factors counted with multiplicity. Analogously to the observation of Lichtman [8], we find that the conjecture is false for q = 2, 3, and 4 by direct numerical computation in Section 6.3. However, in this section we will show that for each k, there exists q k such that the inequality holds up to F (I k,q ) for all q ≥ q k , and we will establish an upper bound on the size of q k .…”
Section: The Banks-martin Inequalitysupporting
confidence: 81%
“…Here the interchange of sum and integral holds by Tonelli's theorem, since f (N k , h) ≤ f (N k ) converges uniformly after Erdős. The significance of the identity (2.1) was first observed when k = 1, h = 0 by H. Cohen [2, p.6], who rapidly computed f (N 1 ) = 1.636616 In general for k ≥ 1, Proposition 3.1 in [6] gives an explicit formula for P k in terms of P ,…”
Section: Proof Of Theoremmentioning
confidence: 99%
“…We have already verified the claim directly for k ≤ 20, since in this case h k ≤ h 2 = 1.04 • • • . For k > 20, the proof strategy is similar to that of Theorem 5.5 in [6]. That is, the integral f (N k , h) = ∞ 1 P k (s)e (1−s)h ds has its mass concentrated near 1 as k → ∞, so it suffices to truncate the integration to [1, 1.01] say, as a lower bound.…”
Section: Proof Of Theoremmentioning
confidence: 99%
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“…uniformly for x ≥ 3 and k ≤ (2 − δ) log 2 x. Then by partial summation, ( 6) implies (5) with constant coefficient…”
Section: Introductionmentioning
confidence: 99%