  We study the existence of homoclinic type solutions for second order
Lagrangian systems of the type $\ddot{q}(t)-q(t)+a(t)\nabla G(q(t))=f(t)$,
where $t\in\mathbb{R}$, $q\in\mathbb{R}^n$, $a\colon\mathbb{R}\to\mathbb{R}$ is
a continuous positive bounded function, $G\colon\mathbb{R}^n\to\mathbb{R}$ is a
$C^1$-smooth potential satisfying the Ambrosetti-Rabinowitz superquadratic
growth condition and $f\colon\mathbb{R}\to\mathbb{R}^n$ is a continuous bounded
square integrable forcing term. A homoclinic type solution is obtained as limit
of $2k$-periodic solutions of an approximative sequence of second order
differential equations.
