4Clojure #97: Pascal's triangle

177.clj

(fn [string]
  (let [br (re-seq #"[()\[\]{}]" string)]
    (loop [brackets br acc []]
      (if (empty? brackets)
        true
        (if-let [lb (#{"(" "[" "{"} (first brackets))]
          (recur (rest brackets) (conj acc lb))
          (if (= (peek acc) ({")" "(" "}" "{" "[" "]"} (first brackets)))
            (recur (rest brackets) (pop acc))
            false))))))

pascal.clj

(defn fact [n]
  (loop [n n acc 1]
    (if (zero? n)
      acc
      (recur (dec n) (* n acc)))))

(defn n-choose-k [n k]
  (/ (fact n) (* (fact k) (fact (- n k)))))

(defn pascal-row [n]
  (for [el (range (inc n))
    	:let [i (n-choose-k n el)]]
    i))