It given that

Why dont you get started by solving the equality:

or else

Next assume that:

By expanding the equation [3] we have that

Since all are possitive integers we compare addition terms seperate:

for any

for any

for any

So we conclude that

for a>1

Finally if a=1 then

The last cannot hold because

So there is no such combination of positive integers that satisfy [1] and [2] conditions