A010848 Number of numbers k <= n such that at least one prime factor of n is not a prime factor of k.

0, 1, 2, 2, 4, 5, 6, 4, 6, 9, 10, 10, 12, 13, 14, 8, 16, 15, 18, 18, 20, 21, 22, 20, 20, 25, 18, 26, 28, 29, 30, 16, 32, 33, 34, 30, 36, 37, 38, 36, 40, 41, 42, 42, 42, 45, 46, 40, 42, 45, 50, 50, 52, 45, 54, 52, 56, 57, 58, 58, 60, 61, 60, 32, 64, 65, 66, 66, 68, 69, 70, 60

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• easy

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A008479, A010846, A010847.

Programs

Maple

f:= n -> n - n/convert(numtheory:-factorset(n),`*`):
map(f, [$1..100]); # Robert Israel, Apr 10 2018

Formula

a(n) = n-A003557(n). - Vladeta Jovovic, Sep 15 2006

Extensions

Definition corrected by Vladeta Jovovic, Sep 15 2006