Do you have some background context for your problem? Is this function a subset of a more general set of results?
Well the general chapter title is Dirichlet's theorem on primes in arithmetic progressions.
I think I am meant to be using similar theory to that of proving a different theorem, whereby we used the introduction of a(n) to replace the summation part and A(x) by sums over n <= x. Then we replace a(n)logn/n.
Does this look familiar at all? I cant say im comfortable with the whole thing.