|
%I #16 Aug 18 2018 16:13:00
%S 2,4,11,31,309,1028,12251,43390,564163,28192750,105097565,5586502348,
%T 80316571436,305761713237,4461632979717,252252704148404,
%U 14458792895301660,55890484045084135,3249254387052557215,48995571600129458363,190499823401327905601
%N Number of primes < 2^prime(n).
%H Gord Palameta, <a href="/A086690/b086690.txt">Table of n, a(n) for n = 1..23</a>
%H Tomás Oliveira e Silva, <a href="http://www.ieeta.pt/%7Etos/primes.html">Tables of values of pi(x) and of pi2(x)</a>
%F a(n) = A007053(A000040(n)).
%e There are 11 primes < 2^5.
%t Table[ PrimePi[ 2^Prime[n]], {n, 1, 14}]
%o (PARI) primesless2p(n) = \primes less than 2^p { forprime(x=2,n, y=pi(2^x); print1(y","); ); print(); print(sr) } pi(n) = { c=0; forprime(x=2,n,c++); return(c) }
%Y Cf. A007053.
%K nonn
%O 1,1
%A _Cino Hilliard_, Jul 28 2003
%E Extended by _Robert G. Wilson v_, Jul 30 2003
%E Revised by _Max Alekseyev_, Jul 20 2007
|
