1,2

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

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

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

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

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

(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

Sequence in context: A305397 A316627 A099801 * A196266 A112232 A168389

Adjacent sequences: A099799 A099800 A099801 * A099803 A099804 A099805

nonn,easy

N. J. A. Sloane, Nov 19 2004

More terms from Emeric Deutsch, Apr 12 2005

approved