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 A000879 Number of primes < prime(n)^2. 18
 2, 4, 9, 15, 30, 39, 61, 72, 99, 146, 162, 219, 263, 283, 329, 409, 487, 519, 609, 675, 705, 811, 886, 1000, 1163, 1252, 1294, 1381, 1423, 1523, 1877, 1976, 2141, 2190, 2489, 2547, 2729, 2915, 3043, 3241, 3436, 3512, 3868, 3945, 4089, 4164, 4627, 5106 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is the least index i such that A052180(i) = prime(n). - Labos Elemer, May 14 2003 Number of primes determined at the n-th step of the sieve of Eratosthenes. - Jean-Christophe HervĂ©, Oct 21 2013 There are only 3 squares in the current data: 4, 9, 7745089. - Michel Marcus, Apr 07 2018 There are no other squares up to a(780000). - Giovanni Resta, Apr 09 2018 LINKS Donovan Johnson, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A000720(A001248(n)). - Michel Marcus, Apr 07 2018 MATHEMATICA PrimePi[Prime[Range[50]]^2] (* Harvey P. Dale, Jan 16 2013 *) PROG (PARI) a(n) = primepi(prime(n)^2); \\ Michel Marcus, Oct 28 2013 CROSSREFS Cf. A050216 (first differences), A089609, A052180, A000720, A001248, A000885, A054270 (primes of rank a(n)) Sequence in context: A266647 A085683 A083270 * A262232 A321410 A218912 Adjacent sequences:  A000876 A000877 A000878 * A000880 A000881 A000882 KEYWORD nonn AUTHOR gandalf(AT)hrn.office.ssi.net (James D. Ausfahl) EXTENSIONS Edited by Ralf Stephan, Aug 24 2004 STATUS approved

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Last modified October 16 08:15 EDT 2019. Contains 328051 sequences. (Running on oeis4.)