(define (sumLast k n)
  (define (helper s currList)
    (let* ((currentList (if (< (length currList) n) (cons s currList)
                                                     (cons s (take currList (- n 1)))))
          (value (foldr + 0 currentList)))
    (stream-cons value (helper value currentList))))
   (stream-cons k (helper k '())))