A060967 Number of squared primes <= 2^n.

0, 0, 1, 1, 2, 3, 4, 5, 6, 8, 11, 14, 18, 24, 31, 42, 54, 72, 97, 128, 172, 229, 309, 418, 564, 760, 1028, 1393, 1900, 2585, 3512, 4792, 6542, 8952, 12251, 16777, 23000, 31579, 43390, 59631, 82025, 112957, 155611, 214516, 295947, 408493, 564163, 779638

Offset: 0

Author

Labos Elemer, May 09 2001

Keywords

• nonn

Examples

			For n = 8, the squared primes not exceeding 2^8 = 256 are 4, 9, 25, 49, 121, 169, so a(8) = 6.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 0..150 (terms 0..63 from Harry J. Smith, terms 64..112 from Hiroaki Yamanouchi, terms 113..125 from Ray Chandler)
• Index entries for sequences related to numbers of primes in various ranges.

Crossrefs

Cf. A000720, A001248, A007053, A017910, A036386, A060969, A060970, A060971, A122121.

Programs

Mathematica

Table[ PrimePi[ Floor[ 2^(g/2)//N ] ], {g, 1, 75} ]

PARI

a(n) = { primepi(sqrtint(2^n)) } \\ Harry J. Smith, Jul 15 2009

Formula

a(2*n) = A007053(n). - Amiram Eldar, Jul 10 2024

a(n) = A000720(A017910(n)). - Amiram Eldar, Mar 22 2025

Extensions

a(0) prepended by Harry J. Smith, Jul 15 2009