A144774 Number of positive integers k less than n such that rad(k) < rad(n).

0, 1, 2, 1, 4, 5, 6, 1, 4, 9, 10, 7, 12, 13, 14, 1, 16, 8, 18, 12, 20, 21, 22, 8, 7, 25, 5, 19, 28, 29, 30, 1, 32, 33, 34, 11, 36, 37, 38, 17, 40, 41, 42, 28, 24, 45, 46, 11, 17, 19, 50, 35, 52, 11, 54, 26, 56, 57, 58, 40, 60, 61, 33, 1, 64, 65, 66, 46, 68, 69, 70, 12, 72, 73, 31, 52, 76

Offset: 1

Author

Reikku Kulon, Sep 21 2008

Keywords

• easy
• nonn

Comments

a(n) = n - 1 if n is a product of distinct primes, since these have rad(n) = n.

Examples

			rad(1) = 1 and rad(2) = 2, so a(2) = 1.
rad(4) is also 2, so a(4) = 1.
rad(12) = 6. The integers k less than 12 for which rad(k) < 6 are 1, 2, 3, 4, 5, 8 and 9. a(12) = 7.
		

Crossrefs

Cf. A007947