Show that is impossible.
My guess would be to start by assuming and try to find a contradiction.
would be true if 15 is prime. But it is not. .
Not sure where to go after this. Any help is appreciated.
Let
Clearly, the factor 7 in 14 cannot come from because 8 and 15 are not prime. Edit: On second thoughts, I guess there could be a like 29, so this proof is no longer valid.
So n must be divisible by 49 and
But then would be divisible by 7-1 = 6, which is a contradiction.