  If $S$ is a numerical semigroup, let $m(S,k)$ denote the number of ideals of
$S$ with codimension $k$ and let $n(S,k)$ denote the number of ideals of $S$
with conductor $k$. We compute the generating function of the sequence $m(S,k)$
for all numerical semigroups of embedding dimension $2$ and for $S = \langle
3,n+2,2n+1\rangle$. We also prove that the sequence $n(S,k)$ becomes stationary
after a certain term and compute the stationary terms for numerical semigroups
of the form $\langle a,a+1 \rangle$.
