Hindawi Publishing Corporation Journal of Discrete Mathematics Volume 2013, Article ID 491627, 11 pages http://dx.doi.org/10.1155/2013/491627 Research Article Efficient Prime Counting and the Chebyshev Primes Michel Planat1 and Patrick Solé2,3 1 Institut FEMTO-ST, CNRS, 32 Avenue de l’Observatoire, F-25044 Besanc¸on, France 2 Telecom ParisTech, 46 rue Barrault, 75634 Paris Cedex 13, France 3 Mathematical Department, King Abdulaziz University, Jeddah, Saudi Arabia Correspondence should be addressed to Michel Planat;
[email protected] Received 17 October 2012; Revised 28 January 2013; Accepted 29 January 2013 Academic Editor: Pantelimon Stanicˇ aˇ Copyright © 2013 M. Planat and P. Sole.´ This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The function () = li() − (), where li is the logarithm integral and () thenumberofprimesupto, is well known to be positive up to the (very large) Skewes’ number. Likewise, according to Robin’s work, the functions () = li[()] − () and () = li[()] − () ,where and are Chebyshev summatory functions, are positive if and only if Riemann hypothesis (RH) holds. One introduces the jump function = li() − li(−1)at primes and one investigates , (),and().Inparticular, 11 <1,and() >1for <10 . Besides, () <1for any odd ∈Ch, an infinite set of the so-called Chebyshev primes.Inthe context of RH, we introduce the so-called Riemann primes as champions of the function ()− (or of the function ()−). 1/ Finally, we find a good prime counting function () = ∑=1(()/) li[() ], that is found to be much better than the standard Riemann prime counting function.