  We consider $\mathcal{A}$-finite map germs $f$ from $(\mathbb{C}^n,0)$ to
$(\mathbb{C}^{2n},0)$. First, we show that the number of double points that
appears in a stabilization of $f$, denoted by $d(f)$, can be calculated as the
length of the local ring of the double point set $D^2(f)$ of $f$, given by the
Mond's ideal. In the case where $n\leq 3$ and $f$ is quasihomogeneous, we also
present a formula to calculate $d(f)$ in terms of the weights and degrees of
$f$. Finally, we consider an unfolding $F(x,t) = (f_t(x),t)$ of $f$ and we find
a set of invariants whose constancy in the family $f_t$ is equivalent to the
Whitney equisingularity of $F$. As an application, we present a formula to
calculate the Euler obstruction of the image of $f$.
