p is prime and .
Then, from here, we subtract 1 because the highest factor is .
Just read the factors can't divide n.
We know that .
Therefore, we must subtract
31 are the number of multiple of 2s, 19 are the multiple of 3s, and 19 are the multiples of 6.
However, this includes some overlap. Your job is to figure out how many to add back in.