Let d(n) be the divisor function. In 1916, S. Ramanujan stated without proof that , where P(y) is a cubic polynomial in y and , with ε being a sufficiently small positive constant. He also stated that, assuming the Riemann Hypothesis (RH), . In 1922, B. M. Wilson proved the above result unconditionally. The direct application of the RH would produce . In 2003, K. Ramachandra and A. Sankaranarayanan proved the above result without any assumption. In this paper, we prove .
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-aa164-2-7, author = {Chaohua Jia and Ayyadurai Sankaranarayanan}, title = {The mean square of the divisor function}, journal = {Acta Arithmetica}, volume = {166}, year = {2014}, pages = {181-208}, zbl = {1320.11081}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-aa164-2-7} }
Chaohua Jia; Ayyadurai Sankaranarayanan. The mean square of the divisor function. Acta Arithmetica, Tome 166 (2014) pp. 181-208. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-aa164-2-7/