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Number of primes <= 3^n.
12

%I #24 Nov 06 2014 09:53:12

%S 0,2,4,9,22,53,129,327,847,2227,5968,16097,43934,120739,334349,931260,

%T 2607165,7332159,20700806,58648288,166677978,475023803,1357200840,

%U 3886548158,11152818693,32064929886,92349038518,266398236486,769616513836,2226457080707,6449247674296,18703411700669,54301968156067,157820174545456

%N Number of primes <= 3^n.

%H Henri Lifchitz, <a href="/A055729/b055729.txt">Table of n, a(n) for n = 0..49</a>

%H <a href="/index/Pri#primepop">Index entries for sequences related to numbers of primes in various ranges</a>

%F a(n) = A000720(A000244(n)). - _Michel Marcus_, Aug 25 2014

%t Table[PrimePi[3^n], {n, 0, 29}]

%o (PARI) a(n) = primepi(3^n); \\ _Michel Marcus_, Aug 25 2014

%Y Cf. A006880 and A007053.

%K nonn

%O 0,2

%A _Robert G. Wilson v_, Jun 09 2000

%E a(28)-a(40) from _Henri Lifchitz_, Nov 11 2012