(defn avg [a] (/ (reduce + a) (count a)))

(defn sq [a] (* a a))

(defn variance [a]
    (let [m (avg a)
        sqd (fn [x] (sq (- x m)))]
        (avg (map sqd a)))
)

(defn lazyvar
    ([n s] (lazyvar n s 0))
    ([n s c] (lazy-seq (cons
        (variance (take n (drop c s)))
        (lazyvar n s (inc c)))))
)

(take 10 (lazyvar 5 (map (fn [a] (* a a)) (range))))