17 lines
580 B
Text
17 lines
580 B
Text
;; using (sum-divisors) from math.lib
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(lib 'math)
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(define (amicable N)
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(define n 0)
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(for/list ((m (in-range 2 N)))
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(set! n (sum-divisors m))
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#:continue (>= n (* 1.5 m)) ;; assume n/m < 1.5
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#:continue (<= n m) ;; prevent perfect numbers
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#:continue (!= (sum-divisors n) m)
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(cons m n)))
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(amicable 20000)
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→ ((220 . 284) (1184 . 1210) (2620 . 2924) (5020 . 5564) (6232 . 6368) (10744 . 10856) (12285 . 14595) (17296 . 18416))
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(amicable 1_000_000) ;; 42 pairs
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→ (... (802725 . 863835) (879712 . 901424) (898216 . 980984) (947835 . 1125765) (998104 . 1043096))
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