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  • 1 Université Laval Dép. de mathématiques et de statistique Québec Québec G1V 0A6 Canada
  • 2 Santiago de Querétaro Mathematical Institute, UNAM, Juriquilla 76230 Querétaro de Arteaga Mexico
  • 3 University of the Witwatersrand School of Mathematics P. O. Box Wits 2050 Witwatersrand South Africa
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For a large class of arithmetic functions f, it is possible to show that, given an arbitrary integer κ ≤ 2, the string of inequalities f(n + 1) < f(n + 2) < … < f(n + κ) holds for in-finitely many positive integers n. For other arithmetic functions f, such a property fails to hold even for κ = 3. We examine arithmetic functions from both classes. In particular, we show that there are only finitely many values of n satisfying σ2(n − 1) < σ2 < σ2(n + 1), where σ2(n) = ∑d|n d 2. On the other hand, we prove that for the function f(n) := ∑p|n p 2, we do have f(n − 1) < f(n) < f(n + 1) in finitely often.

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