Clojure=> (selections [1 2 3] 1)
((1) (2) (3))
Clojure=> (selections [1 2 3] 2)
((1 1) (1 2) (1 3) (2 1) (2 2) (2 3) (3 1) (3 2) (3 3))
Clojure=> (selections [1 1 2] 2)
((1 1) (1 1) (1 2) (1 1) (1 1) (1 2) (2 1) (2 1) (2 2))