euler_67.clj

(defn max-adjacents [coll] 
  (map max coll (rest coll)))

(defn sum-of [prev current] 
  (map + current (max-adjacents prev)))

(defn max-path-sum [tree] 
  (first (reduce sum-of (reverse tree))))

;; To test use the following

;; (def tree  [[3]
;;            [7 4]
;;           [2 4 6]
;;          [8 5 9 3]]

;; (max-path-sum tree)