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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) = Min{x : A052180[x] = p(n) = A000040(n)}. E.g. n = 4: a(4) = 15 since p(4) = 7 occurs first in A052180 as the term with subscript 15, A052180(15) = A052180(A083270[4]) = A000040(4) = 7. - Labos Elemer, May 14 2003

Number of primes determined at the n-th step of the Eratosthenes' sieve. - Jean-Christophe Hervé, Oct 21 2013

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..10000

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 (gives first difference), A089609, A052180, A000720, A000885, A054270 (primes of rank a(n))

Sequence in context: A266647 A085683 A083270 * A262232 A218912 A230868

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 March 29 18:39 EDT 2017. Contains 284273 sequences.