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%I #10 Feb 18 2019 04:08:26
%S 5,14,15,20,26,30,33,35,37,39,40,45,52,55,56,60,62,63,66,70,73,75,81,
%T 87,88,89,91,93,94,96,97,98,101,108,112,115,120,122,125,131,135,140,
%U 143,155,157,166,167,168,171,175,182,183,184,185,188,189,191,192,193,196
%N Centuries containing a prime number of primes.
%H H. v. Eitzen, <a href="/A160709/b160709.txt">Table of n, a(n) for n = 1..10000</a>
%F {n: A038822(n) is in A000040}.
%e a(1) = 5 because 5 is the first Century to have a prime number (17) of primes.
%p A038822 := proc(n) numtheory[pi](n*100)-numtheory[pi]((n-1)*100) ; end: A160709 := proc(n) option remember ; local a; if n = 1 then 5 ; else for a from procname(n-1)+1 do if isprime( A038822(a) ) then RETURN(a) ; fi; od: fi; end: seq(A160709(n),n=1...90) ; # _R. J. Mathar_, May 27 2009
%t Select[Range[200],PrimeQ[PrimePi[100#]-PrimePi[100(#-1)]]&] (* _Harvey P. Dale_, Oct 03 2011 *)
%Y Cf. A000040, A038822.
%K easy,nonn
%O 1,1
%A _Jonathan Vos Post_, May 25 2009
%E Extended by _Ray Chandler_, May 25 2009
%E More terms from _R. J. Mathar_, May 27 2009