OFFSET
1,3
EXAMPLE
The distinct primes which divide 20 are 2 and 5. So a(20) is the number of positive integers < 20 which are not divisible by at least 2 distinct primes dividing 20; i.e. are not divisible by both 2 and 5. Among the first 19 positive integers only 10 is divisible by both 2 and 5. There are 18 other positive integers <= 19, so a(20)=18.
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Jun 20 2007
EXTENSIONS
More terms from Joshua Zucker, Jul 18 2007
STATUS
approved