%I A006879 M3577
%S A006879 0,4,21,143,1061,8363,68906,586081,5096876,45086079,404204977,3663002302,
%T A006879 33489857205,308457624821,2858876213963,26639628671867,249393770611256,
%U A006879 2344318816620308,22116397130086627,209317712988603747,1986761935284574233,
               18906449883457813088,180340017203297174362
%N A006879 Number of primes with n digits.
%C A006879 Also, the number of primes between 10^(n-1) and 10^n. - Cino Hilliard 
               (hillcino368(AT)hotmail.com), May 31 2008 (Corrected by Jon Schoenfield, 
               Nov 29 2008)
%D A006879 J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 21, pp 8, Ellipses, 
               Paris 2008.
%D A006879 C. T. Long, Elementary Introduction to Number Theory. Prentice-Hall, 
               Englewood Cliffs, NJ, 1987, p. 77.
%D A006879 P. Ribenboim, The Book of Prime Number Records. Springer-Verlag, NY, 
               2nd ed., 1989, p. 179.
%D A006879 D. Shanks, Solved and Unsolved Problems in Number Theory. Chelsea, NY, 
               2nd edition, 1978, p. 15.
%D A006879 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A006879 C. K. Caldwell, <a href="http://www.utm.edu/research/primes/howmany.shtml">
               How Many Primes Are There?</a>
%H A006879 <a href="Sindx_Pri.html#primepop">Index entries for sequences related 
               to numbers of primes in various ranges</a>
%H A006879 Cino Hilliard <a href="http://docs.google.com/Doc?id=dgpq9w4b_11m7tc9r">
               Count,Sum primes in a range Win32 Gcc+Gmp</a>.
%F A006879 a(n) = pi(10^n)-pi(10^(n-1)) where pi(10^(-1)) := 0 (cf. A000720).
%e A006879 As 2,3,5 and 7 are the only primes less than 10 the term a(1) = 4.
%Y A006879 First differences of A006880.
%Y A006879 Sequence in context: A120368 A053482 A158577 this_sequence A163861 A006153 
               A025164
%Y A006879 Adjacent sequences: A006876 A006877 A006878 this_sequence A006880 A006881 
               A006882
%K A006879 nonn,base,hard
%O A006879 0,2
%A A006879 N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
%E A006879 11-th and 12th terms corrected by Jud McCranie (j.mccranie(AT)comcast.net) 
               and Enoch Haga (Enokh(AT)comcast.net); 19th term corrected and 20th 
               term added by Paul.Zimmermann(AT)loria.fr (Paul Zimmermann).
%E A006879 Two more terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 07 2001