Clojure is a dynamic, functional, programming language. As a Lisp dialect with immutable data structures it enables multithreaded designs. Clojure appeared as an open-source project in 2007, initiated by Rich Hickey.

(defn fib-step [[a b]]
  [b (+ a b)])

(defn fib-seq []
  (map first (iterate fib-step [0 1])))

(take 10 (fib-seq))
;; => (0 1 1 2 3 5 8 13 21 34)