The ornamental design for a pan, as shown and described.
FIG. 1 is a perspective view showing my new design for a pan,
FIG. 2 is a front view thereof,
FIG. 3 is a rear view thereof,
FIG. 4 is a left side view thereof,
FIG. 5 is a right side view thereof,
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The portions shown in dotted lines are for illustrative purposes only and show a handle cooperating with the pan of the present invention, and form no part of the claimed design.