Sieve of Eratosthenes in Clojur

eratosthenes.clj

(defn eratosthenes
  "finding all prime numbers up to `x`"
  [x]
  (letfn [(continue? [x list]
            (< (first list) (Math/sqrt x)))
          (go [x list primes]
            (if (continue? x list)
              (let [head (first list)
                    new-list (filter #(not (= (mod %1 head) 0)) (rest list))]
                (recur x new-list (cons head primes)))
              (concat primes list)))]
    (go x (range 2 x) '())))