A090972 - OEIS

A090972

Least k such that there are at least n primes between n and n*k.

3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

a(9) = 5 is saying that there are 9 primes between 9 and 45, but actually there are 10: 11, 13, 17, 19, 23, 29, 31, 37, 41, 43. - Michel Marcus, Nov 20 2017

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

a(11) = 5 as there are 11 primes (13,17,19,23,29,31,37,41,43,47,53) between 11 and 55.

PROG

(PARI) a(n) = {k=2; while(sum(i=n+1, k*n-1, isprime(i)) < n, k++); k; } \\ Michel Marcus, Nov 22 2017

CROSSREFS

Sequence in context: A282623 A090589 A163400 * A318241 A181742 A179843

Adjacent sequences: A090969 A090970 A090971 * A090973 A090974 A090975

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Jan 03 2004

EXTENSIONS

More terms from John W. Layman, Jan 20 2004

Name clarified by Alois P. Heinz, Nov 22 2017

Corrected by Michel Marcus, Nov 23 2017

STATUS

approved