A065313 a(n) = pi(n*pi(n)).

0, 1, 3, 4, 6, 7, 9, 11, 11, 12, 16, 17, 21, 23, 24, 24, 30, 30, 36, 37, 39, 40, 46, 47, 48, 51, 53, 54, 61, 62, 68, 70, 72, 74, 76, 77, 86, 87, 91, 92, 99, 100, 110, 112, 114, 117, 126, 128, 130, 132, 135, 137, 146, 150, 151, 154, 156, 157, 168, 171, 184, 186, 189

Offset: 1

Author

Labos Elemer, Oct 29 2001

Keywords

• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000040, A000720, A128913.

Programs

Mathematica

Table[PrimePi[w*PrimePi[w]], {w, 1, 100}]

PARI

a(n) = { primepi(n*primepi(n)) } \\ Harry J. Smith, Oct 16 2009

Formula

a(n) = A000720(n*A000720(n)).