A087266 a(n) = gcd(2^n, pi(2^n)) = gcd(A000079(n), A007053(n)).

1, 2, 4, 2, 1, 2, 1, 2, 1, 4, 1, 4, 4, 4, 8, 2, 1, 8, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 1, 1, 2, 1, 1, 1, 4, 4, 2, 4, 4, 1, 1, 4, 2, 1, 1, 2, 2, 1, 8, 1, 4, 16, 1, 2, 4, 2, 4, 2, 1, 1, 8, 1, 4, 1, 1, 2, 16, 1, 1, 1, 1, 4, 1, 1, 4, 8, 1, 4, 4, 8, 4, 4, 2, 1, 1, 2, 4, 8, 16, 2

Offset: 1

Author

Labos Elemer, Sep 16 2003

Keywords

• nonn

Crossrefs

Cf. A000720, A007053.

Programs

Mathematica

Table[GCD[2^n, PrimePi[2^n]], {n, 40}] (* Michael De Vlieger, Mar 25 2017 *)

PARI

a(n) = gcd(2^n, primepi(2^n)); \\ Michel Marcus, Mar 26 2017

Extensions

a(53)-a(92) from Amiram Eldar, Jun 09 2024