>tilly-powersets A B C D >tilly-powersets A B C D ABCD: skip? n ABCD: skip? n ABC: skip? n ABC: skip? n AB: skip? n AB: skip? n A: skip? n A: skip? n B: skip? n B: skip? y AC: skip? n AC: skip? n C: skip? n C: skip? y BC: skip? n BC: skip? y ABD: skip? n ABD: skip? n AD: skip? n AD: skip? n D: skip? n D: skip? y BD: skip? n BD: skip? y ACD: skip? n ACD: skip? n CD: skip? n CD: skip? y BCD: skip? n BCD: skip? y Done Done