练习3-71

原文

代码

(define (Ramanujan s)
         (define (stream-cadr s) (stream-car (stream-cdr s)))
         (define (stream-cddr s) (stream-cdr (stream-cdr s)))
         (let ((scar (stream-car s))
                   (scadr (stream-cadr s)))
                (if (= (sum-triple scar) (sum-triple scadr))
                        (cons-stream (list (sum-triple scar) scar scadr)
                                                 (Ramanujan (stream-cddr s)))
                        (Ramanujan (stream-cdr s)))))
(define (triple x) (* x x x))
(define (sum-triple x) (+ (triple (car x)) (triple (cadr x))))
(define Ramanujan-numbers
        (Ramanujan (weighted-pairs integers integers sum-triple)))

所以接下来的5个数是：

(4104 (2 16) (9 15))

(13832 (2 24) (18 20))

(20683 (10 27) (19 24))

(32832 (4 32) (18 30))

(39312 (2 34) (15 33))