715,739 research outputs found

    The Nicolas and Robin inequalities with sums of two squares

    Get PDF
    In 1984, G. Robin proved that the Riemann hypothesis is true if and only if the Robin inequality σ(n)<eγnloglogn\sigma(n)<e^\gamma n\log\log n holds for every integer n>5040n>5040, where σ(n)\sigma(n) is the sum of divisors function, and γ\gamma is the Euler-Mascheroni constant. We exhibit a broad class of subsets \cS of the natural numbers such that the Robin inequality holds for all but finitely many n\in\cS. As a special case, we determine the finitely many numbers of the form n=a2+b2n=a^2+b^2 that do not satisfy the Robin inequality. In fact, we prove our assertions with the Nicolas inequality n/ϕ(n)<eγloglognn/\phi(n)<e^{\gamma}\log \log n; since σ(n)/n1\sigma(n)/n1 our results for the Robin inequality follow at once.Comment: 21 page
    corecore