On Thu, Sep 13, 2012 at 10:23:04AM +0300, Georgi Guninski wrote: > |psi(x)-x| < sqrt(x) log^2 x / (8 pi) if x>73.2 > Reference: Sharper bounds for the Chebyshev functions $ \theta (x)$ and $ \psi (x)$. II http://www.ams.org/journals/mcom/1976-30-134/S0025-5718-1976-0457374-X/S0025-5718-1976-0457374-X.pdf