The ornamental design for a fan, as shown and described.
1.-2. Fan
1.1 : Front
1.2 : Back
1.3 : Left
1.4 : Top
1.5 : Bottom
1.6 : Perspective
1.7 : Perspective
2.1 : Front
2.2 : Back
2.3 : Left
2.4 : Top
2.5 : Bottom
2.6 : Perspective
2.7 : Perspective
1.1 is a front elevation view of a first design of fan showing our new design; 1.2 is a rear elevation view thereof; 1.3 is a left side elevation view thereof; 1.4 is a top plan view thereof; 1.5 is a bottom plan view thereof; 1.6 is a perspective view thereof; 1.7 is a perspective view thereof; 2.1 is a front elevation view of a second design of fan showing our new design; 2.2 is a rear elevation view thereof; 2.3 is a left side elevation view thereof; 2.4 is a top plan view thereof; 2.5 is a bottom plan view thereof; 2.6 is a perspective view thereof; and 2.7 is a perspective view thereof; the present products are used for blowing air, heat radiating and ventilating.