Let be the Divisor Function. Then
References
Berndt, B. C. Ramanujan's Notebooks: Part I. New York: Springer-Verlag, p. 94, 1985.
Gronwall, T. H. ``Some Asymptotic Expressions in the Theory of Numbers.'' Trans. Amer. Math. Soc. 37, 113-122, 1913.
Nicholas, J.-L. ``On Highly Composite Numbers.'' In Ramanujan Revisited: Proceedings of the Centenary Conference
(Ed. G. E. Andrews, B. C. Berndt, and R. A. Rankin). Boston, MA: Academic Press, pp. 215-244, 1988.
Robin, G. ``Grandes Valeurs de la fonction somme des diviseurs et hypothèse de Riemann.'' J. Math. Pures Appl. 63, 187-213, 1984.