Fan

FIG. 1 is a front, top perspective view of a fan, showing my new design; FIG. 2 is a rear, bottom perspective view thereof; FIG. 3 is a front elevation view thereof; FIG. 4 is a rear elevation view thereof; FIG. 5 is a left side elevation view thereof; FIG. 6 is a right side elevation view thereof; FIG. 7 is a top plan view thereof; and, FIG. 8 is a bottom plan view thereof. The broken lines in the figures illustrate portions of the fan that form no part of the claimed design.