fib.clj

(def fibs
  (map first (iterate (fn [[a b]] [b (+ a b)]) [1 1])))

(defn fibs-from [n]
  (drop-while #(< % n) fibs))

(take 5 fibs)
; (1 1 2 3 5)

(take 5 (fibs-from 1000000000000))
; (1548008755920 2504730781961 4052739537881 6557470319842 10610209857723)

(zipmap (range) (take 5 fibs))
; {4 5, 3 3, 2 2, 1 1, 0 1}