%N Number of solutions x to n * pi(x) = x, where pi(x) = number of primes <= x.
%C Equivalently, a(n) is number of solutions x to the equation pi(n*x) = x. - _Farideh Firoozbakht_, Jan 09 2005. For example, a(2) = 4 because 1, 2, 3 & 4 are all solutions of pi(2*x) = x and a(11) = 1 because 15927 is the only solution of the equation pi(11*x) = x.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PrimeCountingFunction.html">Prime Counting Function.</a>
%e 11*pi(x) = x has only 1 solution, so a(11) = 1.
%Y Cf. A038623-A038626, A102281, A087237.
%A _Jud McCranie_
%E Vasiliy Danilov (danilovv(AT)usa.net) proved that solutions exist for each n>1.
%E One more term from Labos E. (labos(AT)ana.sote.hu), Sep 05 2003
%E a(24)-a(26) from Labos E. (labos(AT)ana.sote.hu), Sep 12 2003
%E Edited by _N. J. A. Sloane_, Sep 06 2008 at the suggestion of R. J. Mathar