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  1. ; triperfect numbers
  2.  
  3. (define (factors n)
  4.   (let ((wheel (vector 1 2 2 4 2 4 2 4 6 2 6)))
  5.     (let loop ((n n) (f 2) (w 0) (fs (list)))
  6.       (cond ((< n (* f f)) (reverse (cons n fs)))
  7.             ((zero? (modulo n f))
  8.               (loop (/ n f) f w (cons f fs)))
  9.             (else (loop n (+ f (vector-ref wheel w))
  10.                         (if (= w 10) 3 (+ w 1)) fs))))))
  11.  
  12. (define (divisors n) ; divisors of n, including 1 and n
  13.   (let ((divs (list 1)))
  14.     (do ((fs (factors n) (cdr fs))) ((null? fs) (sort divs <))
  15.       (let ((temp (list)))
  16.         (do ((ds divs (cdr ds)))
  17.             ((null? ds) (set! divs (append divs temp)))
  18.           (let ((d (* (car fs) (car ds))))
  19.             (when (not (member d divs))
  20.               (set! temp (cons d temp)))))))))
  21.  
  22. (define (multi-perfect k)
  23.   (do ((n 1 (+ n 1))) ((= n 1000))
  24.     (when (= (apply + (divisors n)) (* k n))
  25.       (display n) (newline))))
  26.  
  27. (multi-perfect 3)
Success #stdin #stdout 0.31s 51608KB
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https://ideone.com/H4dCfY
language:
Scheme (guile 2.2.4)
created:
4 years ago
visibility:
public

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