Proper divisors: Difference between revisions

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=={{header|Factor}}==

<lang Factor>

USING: math.primes.factors math.ranges ;

10 [1,b] [ divisors but-last ] map [ 1 + pprint bl . ] each-index

20000 [1,b] [ divisors but-last length ] map dup supremum

swap dupd index 1 + pprint " with " write pprint " divisors." print

</lang>

{{out}}

<pre>

1 { }

2 { 1 }

3 { 1 }

4 { 1 2 }

5 { 1 }

6 { 1 2 3 }

7 { 1 }

8 { 1 2 4 }

9 { 1 3 }

10 { 1 2 5 }

15120 with 79 divisors.