Hugh L Montgomery
Articles written in Proceedings – Mathematical Sciences
Volume 97 Issue 1-3 December 1987 pp 239-245
We consider the error term in the mean value estimate of Euler’s phi function ψ(n), and show that it is Ω+- (x(log log x)1/2). This improves on the earlier results of Pillai and Chowla, and of Erdös and Shapiro.