gistfile1.clj

(fn [s e]
  (->> [[s]]
       (iterate #(mapcat (fn [[c :as p]]
                           (for [f [* / +]
                                 :let [n (f c 2)]
                                 :when (integer? n)]
                             (cons n p)))
                         %))
       (map #(filter (comp #{e} first) %))
       (filter seq)
       ffirst
       count))