|
| |
|
|
A131232
|
|
a(n) = number of positive integers < n which don't have 2 or more distinct prime divisors in common with n.
|
|
2
| |
|
|
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 12, 13, 14, 15, 16, 15, 18, 18, 20, 21, 22, 20, 24, 25, 26, 26, 28, 22, 30, 31, 32, 33, 34, 30, 36, 37, 38, 36, 40, 32, 42, 42, 42, 45, 46, 40, 48, 45, 50, 50, 52, 45, 54, 52, 56, 57, 58, 44, 60, 61, 60, 63, 64, 52, 66, 66, 68, 58, 70, 60, 72
(list; graph; refs; listen; history; internal format)
|
|
|
|
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
| Cf. A131233.
Sequence in context: A172268 A017895 A130024 * A010881 A190600 A053832
Adjacent sequences: A131229 A131230 A131231 * A131233 A131234 A131235
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Leroy Quet Jun 20 2007
|
|
|
EXTENSIONS
| More terms from Joshua Zucker (joshua.zucker(AT)stanfordalumni.org), Jul 18 2007
|
| |
|
|
