exe1.31.lsp

(define (even n)(=(remainder n 2) 0))
(define (sum_rec n)
        (define (term a) (if (even a) (/ a (+ a 1)) (/ (+ a 1) a)))
        (define (next a) (+ 1 a))
        (define (s term k next l)
        (if (> k l)
           1
           (* (term k) (s term (next k) next l ))))
        (s term 2 next n))



(define (sum_itr n)
        (define (term a) (if (even a) (/ a (+ a 1)) (/ (+ a 1) a)))
        (define (next a) (+ 1 a))
        (define (siter k result)
        (if (> k n)
            result
            (siter (next k) (* result (term k)))))
        (siter 2 1)