The ornamental design for a fan, as shown and described.
FIG. 1 is an isometric view of a fan in accordance with the present invention;
FIG. 2 is a front elevational view of the fan of FIG. 1;
FIG. 3 is a rear elevational view of the fan of FIG. 1;
FIG. 4 is a side elevational view of a first side of the fan of FIG. 1;
FIG. 5 is a side elevational view of a second side of the fan of FIG. 1;
FIG. 6 is a top plan view of the fan of FIG. 1; and,
FIG. 7 is a bottom plan view of the fan of FIG. 1.
The broken lines in the drawings depict portions of the fan that form no part of the claim.
The claim is directed to the design shown in solid lines and all surfaces shown between the broken lines and solid lines form no part of the claimed design.