  We prove several results about integers represented by positive definite
quadratic forms, using a Fourier analysis approach. In particular, for an
integer $\ell\geq 1$, we improve the error term in the partial sums of the
number of representations of integers multiple of $\ell$. This allows us to
obtain unconditional Brun-Titchmarsh-type results in short intervals, and a
conditional Cram\'er-type result on the maximum gap between primes represented
by a given positive definite quadratic form.
