A063124 a(n) = # { i prime | prime(n) <= i < prime(n)*2 } (prime(n) = A000040, the prime enumeration).

2, 2, 2, 3, 4, 4, 5, 5, 6, 7, 8, 10, 10, 10, 10, 12, 14, 13, 14, 15, 14, 16, 16, 17, 20, 21, 20, 20, 19, 19, 24, 24, 26, 26, 28, 27, 29, 29, 29, 29, 31, 31, 33, 33, 33, 33, 36, 39, 39, 39, 40, 40, 40, 42, 43, 44, 43, 43, 43, 43, 43, 45, 50, 51, 50, 50, 55, 55, 57, 56, 56, 56, 58

Offset

1,1

Comments

a(n) is the number of primes between prime(n) and 2*prime(n) inclusive. - Sean A. Irvine, Apr 18 2023

Links

Harry J. Smith, Table of n, a(n) for n = 1..2000

Formula

a(n) = A035250(prime(n)).

a(n) = A070046(n) + 1. - Sean A. Irvine, Apr 18 2023

Example

a(10) = 7 as there are 7 primes between prime(10) = 29 and 58 = 29*2: 29, 31, 37, 41, 43, 47, 53.

Prog

(PARI) a(n)={1 + primepi(2*prime(n)) - n} \\ Harry J. Smith, Aug 19 2009

Crossrefs

Cf. A035250, A000040, A070046.

Sequence in context: A244988 A105098 A303003 * A358901 A070547 A319922

Adjacent sequences: A063121 A063122 A063123 * A063125 A063126 A063127

Keyword

nonn

Author

Reinhard Zumkeller, Aug 08 2001

Status

approved