A055730 Number of primes <= 5^n.

0, 3, 9, 30, 114, 445, 1821, 7671, 33118, 145713, 650133, 2934858, 13375865, 61444585, 284140656, 1321453490, 6175961983, 28988040005, 136575061279, 645620925545, 3061129684411, 14552990145243, 69354801708586, 331251325552977, 1585299642009257, 7600886353341754, 36504944044424979

Offset: 0

Author

Robert G. Wilson v, Jun 09 2000

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 0..34
• Index entries for sequences related to numbers of primes in various ranges

Crossrefs

Cf. A006880, A007053 and A040014.

Programs

Mathematica

Table[PrimePi[5^n], {n, 0, 19}]

PARI

a(n) = primepi(5^n); \\ Michel Marcus, Aug 25 2014

Formula

a(n) = A000720(A000351(n)). - Michel Marcus, Aug 25 2014

Extensions

a(19) corrected by Henri Lifchitz, Nov 11 2012

a(20)-a(27) from Henri Lifchitz, Nov 11 2012

a(28)-a(32) from Henri Lifchitz, Aug 25 2014

Definition corrected by Jean-Claude Arbaut, Oct 07 2015

a(33) from Robert Price, May 07 2025