The Hardy–Littlewood problem for numbers with a fixed number of prime divisors

In this paper we investigate the number of representations of a natural number $N$ as the sum of a number with $k$ prime divisors and two squares, where $k$ may depend on $N$. We determine the asymptotic behaviour when $2\leqslant k\leqslant(2-\varepsilon)\ln\ln N$ and $(2+\varepsilon)\ln\ln N\leqslant k\leqslant b\ln\ln N$.