(defn random [n]
  (math/floor (* n (math/random))))

(defn square [n]
  (* n n))

(defn divides? [a b]
  (= (mod b a) 0))

(defn expmod [base exp m]
  (cond
    (= exp 0) 1
    (even? exp) (mod (square (expmod base (/ exp 2) m)) m)
    (mod (* base (expmod base (- exp 1) m)) m)))

(defn fermat-test [n]
  (defn iter [a]
    (cond
      (= a 0) true
      (= (expmod a n n) a) (iter (- a 1))
      false))
  (iter (- n 1)))

(print (fermat-test 561))
(print (fermat-test 1105))
(print (fermat-test 1729))
(print (fermat-test 2465))
(print (fermat-test 2821))
(print (fermat-test 6601))