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A099802 Bisection of A000720. 4
1, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 9, 10, 11, 11, 11, 12, 12, 13, 14, 14, 15, 15, 15, 16, 16, 16, 17, 18, 18, 18, 19, 19, 20, 21, 21, 21, 22, 22, 23, 23, 23, 24, 24, 24, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 30, 30, 30, 30, 30, 30, 31, 31, 32, 32, 32, 33, 34, 34, 34, 34, 34 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Maximal number of primes possible in a string of 2n consecutive numbers. - Lekraj Beedassy, Dec 04 2004

a(n) = A139325(n,1) + 1. - Reinhard Zumkeller, Apr 14 2008

Or the number of primes <= 2n. - Juri-Stepan Gerasimov, Oct 29 2009

LINKS

Table of n, a(n) for n=1..74.

FORMULA

a(n) = A000720(n) + A035250(n) - A010051(n). - Reinhard Zumkeller, Jul 05 2010

a(n) = pi(2n). - Wesley Ivan Hurt, Jun 16 2013

MAPLE

with(numtheory):seq(pi(2*n), n=1..86); (Deutsch)

PROG

(Sage) [prime_pi(2*n) for n in xrange(1, 75)] # - Zerinvary Lajos, Jun 06 2009

(PARI) a(n)=primepi(2*n) \\ Charles R Greathouse IV, Sep 02 2015

CROSSREFS

Sequence in context: A305397 A316627 A099801 * A196266 A112232 A168389

Adjacent sequences:  A099799 A099800 A099801 * A099803 A099804 A099805

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Nov 19 2004

EXTENSIONS

More terms from Emeric Deutsch, Apr 12 2005

STATUS

approved

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Last modified August 14 21:07 EDT 2018. Contains 313756 sequences. (Running on oeis4.)