A249058 a(n) = number of primes less than the square root of the (2^n)-th prime.

0, 0, 1, 2, 4, 5, 7, 9, 12, 17, 24, 32, 45, 61, 82, 114, 154, 215, 293, 404, 557, 766, 1057, 1459, 2025, 2800, 3880, 5379, 7470, 10368, 14414, 20030, 27864, 38745, 53982, 75206, 104799, 146151, 203821, 284381, 396976, 554303, 774256, 1081749, 1511871, 2113506

Offset: 0

Author

Russ Cox, Oct 19 2014

Keywords

• nonn

Links

• Hugo Pfoertner, Table of n, a(n) for n = 0..78 (terms 0..56 from Jens Kruse Andersen)

Crossrefs

Cf. A033844. Related to analysis of A247665.

Programs

Mathematica

PrimePi[Sqrt[Prime[2^n]]]

Formula

a(n) = primepi(sqrt(A033844(n))). - Jens Kruse Andersen, Oct 20 2014

Extensions

More terms from Jens Kruse Andersen, Oct 20 2014