Proper divisors: Difference between revisions
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{num:10, divisors:{1, 2, 5}}},
mostDivisors:{num:18480, divisors:79}}</lang>
=={{header|Arc}}==
<lang Arc>
;; Given num, return num and the list of its divisors
(= divisor (fn (num)
(= dlist '())
(when (is 1 num) (= dlist '(1 0)))
(when (is 2 num) (= dlist '(2 1)))
(unless (or (is 1 num) (is 2 num))
(up i 1 (+ 1 (/ num 2))
(if (is 0 (mod num i))
(push i dlist)))
(= dlist (cons num dlist)))
dlist))
;; Find out what number has the most divisors between 2 and 20,000.
;; Print a list of the largest known number's divisors as it is found.
(= div-lists (fn (cnt (o show 0))
(= tlist '()) (= clist tlist)
(when (> show 0) (prn tlist))
(up i 1 cnt
(divisor i)
(when (is 1 show) (prn dlist))
(when (>= (len dlist) (len tlist))
(= tlist dlist)
(when (is show 2) (prn tlist))
(let c (- (len dlist) 1)
(push (list i c) clist))))
(= many-divisors (list ((clist 0) 1)))
(for n 0 (is ((clist n) 1) ((clist 0) 1)) (= n (+ 1 n))
(push ((clist n) 0) many-divisors))
(= many-divisors (rev many-divisors))
(prn "The number with the most divisors under " cnt
" has " (many-divisors 0) " divisors.")
(prn "It is the number "
(if (> 2 (len many-divisors)) (cut (many-divisors) 1)
(many-divisors 1)) ".")
(prn "There are " (- (len many-divisors) 1) " numbers"
" with this trait, and they are "
(map [many-divisors _] (range 1 (- (len many-divisors) 1))))
(prn (map [divisor _] (cut many-divisors 1)))
many-divisors))
;; Do the tasks
(div-lists 10 1)
(div-lists 20000)
;; This took about 10 minutes on my machine.
</lang>
{{Out}}
<lang Arc>
(1 0)
(2 1)
(3 1)
(4 2 1)
(5 1)
(6 3 2 1)
(7 1)
(8 4 2 1)
(9 3 1)
(10 5 2 1)
The number with the most divisors under 10 has 3 divisors.
It is the number 10.
There are 3 numbers with this trait, and they are (10 8 6)
((10 5 2 1) (8 4 2 1) (6 3 2 1))
'(3 10 8 6)
The number with the most divisors under 20000 has 79 divisors.
It is the number 18480.
There are 2 numbers with this trait, and they are (18480 15120)
</lang>
=={{header|AWK}}==
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