(defn fib ([] (concat [0 1] (fib 0 1))) ([a b] (lazy-seq (cons (+ a b) (fib b (+ a b)))))) (println (take 20 (fib))) (def fib-seq ((fn rfib [a b] (lazy-seq (cons a (rfib b (+ a b))))) 0 1)) (println (take 20 fib-seq)) lazy-seq が ポイント…