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%I #20 Jan 15 2023 02:08:53
%S 3,4,5,6,11,12,17,18,31,32,33,34,35,36,41,42,59,60,67,68,69,70,83,84,
%T 85,86,87,88,109,110,111,112,127,128,129,130,157,158,159,160,161,162,
%U 179,180,191,192,211,212,213,214,215,216,217,218,219
%N Numbers k such that pi(k) is prime.
%C A000720(a(n)) is prime. - _Omar E. Pol_, Dec 19 2008
%H T. D. Noe, <a href="/A048989/b048989.txt">Table of n, a(n) for n = 1..10000</a>
%t Select[Range[250],PrimeQ[PrimePi[#]]&] (* _Harvey P. Dale_, Mar 23 2011 *)
%o (PARI) isok(k) = isprime(primepi(k)); \\ _Michel Marcus_, Jan 15 2023
%Y Cf. A000720.
%K nonn,easy,nice
%O 1,1
%A _G. L. Honaker, Jr._
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