Fan

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