On the residue class distribution of the number of prime divisors of an integer

The {\em Liouville function} is defined by $\gl(n):=(-1)^{\Omega(n)}$ where $\Omega(n)$ is the number of prime divisors of $n$ counting multiplicity. Let $\z_m:=e^{2\pi i/m}$ be a primitive $m$--th root of unity. As a generalization of Liouville's function, we study the functions $\gl_{m,k}(n):=\z_m^{k\Omega(n)}$. Using properties of these functions, we give a weak equidistribution result for $\Omega(n)$ among residue classes. More formally, we show that for any positive integer $m$, there exists an $A>0$ such that for all $j=0,1,...,m-1,$ we have $$#\{n\leq x:\Omega(n)\equiv j (\bmod m)\}=\frac{x}{m}+O(\frac{x}{\log^A x}).$$ Best possible error terms are also discussed. In particular, we show that for $m>2$ the error term is not $o(x^\ga)$ for any $\ga<1$.