Project Euler in Clojure

; Problem 1
(apply + (filter #(or (= 0 (mod % 5)) (= 0 (mod % 3))) (range 1000)))

; Problem 2
(defn fib
  ([] (fib 0 1))
  ([n-2 n-1] 
     (lazy-seq (cons n-1 (fib n-1 (+ n-2 n-1))))))

(reduce + (take-while #(< % 4000000) (filter even? (fib))))

; Problem 3
(defn prime-factors [i]
  (or (if-let [smallest-factor (first (filter #(= 0 (mod i %)) (range 2 (. Math sqrt i))))]
	(cons smallest-factor (prime-factors (/ i smallest-factor))))
      (list i)))

(prime-factors 600851475143)

; Problem 4
(defn palindrome? [i]
  (when (even? (count (str i)))
    (let [[first second] (split-at (/ (count (str i)) 2) (str i))]
      (when (= first (reverse second))
	i))))

(apply max (filter palindrome? (for [x (range 1000) y (range 1000)] (* x y))))