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%I #50 Apr 21 2024 23:01:19
%S 2,4,9,15,30,39,61,72,99,146,162,219,263,283,329,409,487,519,609,675,
%T 705,811,886,1000,1163,1252,1294,1381,1423,1523,1877,1976,2141,2190,
%U 2489,2547,2729,2915,3043,3241,3436,3512,3868,3945,4089,4164,4627,5106
%N Number of primes < prime(n)^2.
%C a(n) is the least index i such that A052180(i) = prime(n). - _Labos Elemer_, May 14 2003
%C Number of primes determined at the n-th step of the sieve of Eratosthenes. - _Jean-Christophe Hervé_, Oct 21 2013
%C There are only 3 squares in the current data: 4, 9, 7745089. - _Michel Marcus_, Apr 07 2018
%C There are no other squares up to a(780000). - _Giovanni Resta_, Apr 09 2018
%H Donovan Johnson, <a href="/A000879/b000879.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A000720(A001248(n)). - _Michel Marcus_, Apr 07 2018
%t PrimePi[Prime[Range[50]]^2] (* _Harvey P. Dale_, Jan 16 2013 *)
%o (PARI) a(n) = primepi(prime(n)^2); \\ _Michel Marcus_, Oct 28 2013
%Y Cf. A050216 (first differences), A089609, A052180, A000720, A001248, A000885, A054270 (primes of rank a(n)).
%K nonn,changed
%O 1,1
%A gandalf(AT)hrn.office.ssi.net (James D. Ausfahl)
%E Edited by _Ralf Stephan_, Aug 24 2004
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