  A weakly disordered quasi-one-dimensional tight-binding hopping model with
$N$ rows is considered. The probability distribution of the Landauer
conductance is calculated exactly in the middle of the band, $\epsilon=0$, and
it is shown that a delocalization transition at this energy takes place if and
only if $N$ is odd. This even-odd effect is explained by level repulsion of the
transmission eigenvalues.
