%I A073517
%S A073517 0,4,25,160,1193,9585,80020,686048,6003530,53378283,480532488,
%T A073517 4369582734,40063566855,369893939287,3435376839800,32069022099022,
%U A073517 300694113015105,2830466318006780,26735673312004455,253315661161665338
%N A073517 Number of primes less than 10^n with initial digit 1.
%H A073517 Chris K. Caldwell, <a href="http://www.utm.edu/research/primes/howmany.shtml">
               How Many Primes Are There?</a>
%H A073517 Xavier Gourdan & Pascal Sebah, <a href="http://numbers.computation.free.fr/
               Constants/Primes/countingPrimes.html">Counting the number of primes 
               [sic]</a>
%H A073517 Henri Lifchitz, <a href="http://ourworld.compuserve.com/homepages/hlifchitz/
               Henri/us/ParPius.htm">Parity of Pi(n)</a>
%H A073517 Thomas R. Nicely, <a href="http://www.trnicely.net/index.html">Some Results 
               of Computational Research in Prime Numbers</a>
%e A073517 a(2)=4 because there are 4 primes up to 10^2 whose initial digit is 1 
               (11, 13, 17 and 19).
%t A073517 f[n_] := f[n] = PrimePi[2*10^n] - PrimePi[10^n] + f[n - 1]; f[0] = 0; 
               Table[ f[n], {n, 0, 13}]
%Y A073517 Cf. A073509 to A073517, their sum is A006880.
%Y A073517 Sequence in context: A091634 A010909 A079750 this_sequence A074422 A128419 
               A006880
%Y A073517 Adjacent sequences: A073514 A073515 A073516 this_sequence A073518 A073519 
               A073520
%K A073517 base,hard,nonn
%O A073517 0,2
%A A073517 Shyam Sunder Gupta (guptass(AT)rediffmail.com), Aug 14 2002
%E A073517 Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 29 
               2002