[seqfan] sujet = Re: A071390

Bernard SCHOTT bernardschott at orange.fr
Thu Apr 2 09:13:40 CEST 2020


For p prime, sigma(p) - phi(p) = 2.

For m composite, sigma(m) - phi(m) > sqrt(m), so a convenient bound for m for
"Least number m such that sigma(m) - phi(m) = n " is n^2. The previous proposed
(n/4)^2 is not sufficient (for example with A071390(35) = 289).



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