The ornamental design for a pan, as shown and described.
FIG. 1 is a front side perspective view showing the new design for a pan;
FIG. 2 is a left side view thereof,
FIG. 3 is a right side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a bottom perspective view thereof.
The evenly broken lines are shown for the purpose of illustrating parts of the article that form no part of the claim. The dot-dash lines represent the boundaries of the claim and form no part thereof.