A127197 a(n) = numerator( pi(n)/2^n ).

1, 1, 1, 3, 3, 1, 1, 1, 1, 5, 5, 3, 3, 3, 3, 7, 7, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 5, 5, 11, 11, 11, 11, 11, 11, 3, 3, 3, 3, 13, 13, 7, 7, 7, 7, 15, 15, 15, 15, 15, 15, 1, 1, 1, 1, 1, 1, 17, 17, 9, 9, 9, 9, 9, 9, 19, 19, 19, 19, 5, 5, 21, 21, 21, 21, 21, 21, 11, 11, 11, 11, 23, 23, 23, 23, 23, 23

Offset: 2

Author

Artur Jasinski, Jan 08 2007

Keywords

• nonn
• frac

Crossrefs

Cf. A000079 (2^n), A000720 (PrimePi), A119523.

Programs

Mathematica

Table[Numerator[PrimePi[k]/2^k], {k, 2, 1000}]

PARI

a(n) = numerator(primepi(n)/2^n); \\ Michel Marcus, Oct 28 2019

Extensions

Offset 2 from Michel Marcus, Oct 28 2019

New name using formula from Joerg Arndt, Jan 20 2024