We prove that the error term differs from (ψ(x)-x)/x by a well controlled function. We deduce very precise numerical results from the formula obtained.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-aa159-2-2, author = {Olivier Ramar\'e}, title = {Explicit estimates for the summatory function of $\Lambda$(n)/n from the one of $\Lambda$(n)}, journal = {Acta Arithmetica}, volume = {161}, year = {2013}, pages = {113-122}, zbl = {06164549}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-aa159-2-2} }
Olivier Ramaré. Explicit estimates for the summatory function of Λ(n)/n from the one of Λ(n). Acta Arithmetica, Tome 161 (2013) pp. 113-122. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-aa159-2-2/