

A059316


Least integer m such that between m and 2m (including endpoints) there are exactly n primes.


4



1, 2, 7, 10, 16, 22, 27, 31, 36, 37, 51, 52, 55, 57, 70, 79, 87, 91, 96, 97, 100, 120, 121, 126, 135, 136, 142, 147, 157, 175, 177, 187, 190, 205, 210, 211, 217, 220, 222, 232, 246, 250, 255, 262, 289, 297, 300, 301, 304, 307, 310, 324, 327, 330, 331, 342, 346
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OFFSET

1,2


COMMENTS

See A060756 for the case they are excluded.  R. J. Mathar, Nov 28 2007
A035250(a(n)) = n and A035250(m) <> n for m < a(n). [Reinhard Zumkeller, Jan 08 2012]


LINKS

T. D. Noe, Table of n, a(n) for n=1..1000
A related page [Broken link]
[Warning: As of March 2018 this site appears to have been hacked. Proceed with great caution. The original content should be retrieved from the Wayback machine and added here.  N. J. A. Sloane, Mar 29 2018]
Wilkinson, Erdos' proof of Bertrand's postulate, MathForum(AT)Drexel.


EXAMPLE

a(3)=7 because 7 is the least integer such that between 7 and 14 there are 3 primes.


MATHEMATICA

im[n_]:=Module[{m=1}, While[PrimePi[2m](PrimePi[m1])!=n, m++]; m]; Array[ im, 60] Harvey P. Dale, May 19 2012


PROG

(Haskell)
import Data.List (elemIndex)
import Data.Maybe (mapMaybe)
a059316 n = a059316_list !! n
a059316_list = map (+ 1) $ mapMaybe (`elemIndex` a035250_list) [1..]
 Reinhard Zumkeller, Jan 05 2012


CROSSREFS

Sequence in context: A246128 A343990 A226830 * A295825 A140115 A294865
Adjacent sequences: A059313 A059314 A059315 * A059317 A059318 A059319


KEYWORD

nice,nonn


AUTHOR

Felice Russo, Jan 25 2001


STATUS

approved



