  We generalize the wave functions of the displaced and squeezed number states,
found by Nieto, to a time-dependent harmonic oscillator with variable mass and
frequency. These time-dependent displaced and squeezed number states are
obtained by first squeezing and then displacing the exact number states and are
exact solutions of the Schr\"{o}dinger equation. Further, these wave functions
are the time-dependent squeezed harmonic-oscillator wave functions centered at
classical trajectories.
