сумма ряда. GNU Common Lisp

(defun d (n)
           (do 
             ((result 2))
               ((= n 1) result)
                     (setq result (+ result (/ (+ n 1) n)))
(setq n (- n 1))))
>(d 2)

CL-USER> (defun dd (n)
           (do ((res 2))
               ((= n 1) res)
             (setf res (+ res (/ (1+ n) n)))
             (setf n (1- n))))
                
DD
CL-USER> (dd 2)
7/2

(defun series-sum (n)
  (do ((curr-n 1 next-n)
       (next-n 2 (1+ next-n))
       (result 0 (+ result (/ next-n curr-n))))
      ((< n curr-n) result)))

HomeLisp:
 
(defun task (n)
 (iter (for i from 1 to n) (summing (/ (+ i 1) i))))
 
==> task
 
(task 2)
 
==> 3.5

(defun 2/1+3/2...+[n+1]/n (n)
  (if (zerop n) 0 (+ (/ (1+ n) n) (2/1+3/2...+[n+1]/n (1- n)))))
 
> (2/1+3/2...+[n+1]/n 2)
7/2

(defun 2/1+3/2...+[n+1]/n (n)
  (loop for a from 1 to n summing (/ (1+ a) a)))
 
> (2/1+3/2...+[n+1]/n 2)
7/2