A096359 Numbers formed by the second nesting of pi(10^n).

2, 9, 39, 201, 1184, 7702, 53911, 397557, 3048955, 24106415, 195296943, 1613846646, 13556756261, 115465507935, 995112599484, 8663956207026, 76105984161825, 673776962356604, 6006525919368810, 53878729390812464, 485986685605473234, 4405654516157364292, 40121204955640303216, 366893555203205479291

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Jonathan Bayless, Dominic Klyve, and Tomás Oliveira e Silva, New Bounds and Computations on Prime-Indexed Primes, Integers, Vol.13, July 10, 2013.

Formula

Let pi(n) = the number of primes <= n. Then a(n) = pi(pi(n))

Mathematica

Table[ Nest[ PrimePi, 10^n, 2], {n, 13}] (* Robert G. Wilson v, Jul 01 2004 *)

Prog

(PARI) nestpi(n, m) = { for(x=1, n, z=10^x; for(y=1, m, z=abs(primepi(z))); print1(floor(z)", ")) }

Crossrefs

Cf. A006880, A101225, A101226.

Sequence in context: A151016 A151017 A151018 * A020002 A346687 A120700

Adjacent sequences: A096356 A096357 A096358 * A096360 A096361 A096362

Keyword

nonn

Author

Cino Hilliard, Jun 30 2004

Extensions

a(10) - a(15) from Robert G. Wilson v, Jul 01 2004

a(16) - a(19) from Henri Lifchitz, Nov 11 2012

a(20) - a(24) from Bayless, Table 1, p.7, Jonathan Vos Post, Aug 09 2013

Status

approved