user>  (for [x (range)
         :while (<= x 10)
         y (range x)
         z (range x)
         :let [yz (* y z)]
         :when (= x yz)]
      [x y z])
([4 2 2] [6 2 3] [6 3 2] [8 2 4] [8 4 2] [9 3 3] [10 2 5] [10 5 2])

user>  (for [x (range)
         y (range x)
         :while (<= x 10)
         z (range x)
         :let [yz (* y z)]
         :when (= x yz)]
      [x y z])
; Evaluation aborted. (Won't terminate)