Answer:Any odd multiple of 3 would be the counterexample of the given conjecture.
That is 3(2n - 1), for any natural number n, will be divisible by 3 but not divisible by 6 as 2 is not a factor.
Examples:
3(3) = 9
3(5) = 15
3(7) = 21 are some examples.
Explanation: