Proper divisors: Difference between revisions
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[[], [1], [1], [1, 2], [1], [1, 2, 3], [1], [1, 2, 4], [1, 3], [1, 2, 5]]
15120 has 79 divisors
</pre>
===A Alternative Approach===
<lang ruby>
#Determine the integer within a range of integers that has the most proper divisors
#Nigel Galloway: December 23rd., 2014
require "prime"
n, g = 0
(1..20000).each{|i| e = i.prime_division().inject(1){|n,g| n*=g[1]+1}
n, g = e, i if e > n}
puts "#{g} has #{n-1} proper divisors"
</lang>
{{out}}
In the range 1..200000
<pre>
15120 has 79 proper divisors
</pre>
and in the ranges 1..2000000 & 1..20000000
<pre>
166320 has 159 proper divisors
1441440 has 287 proper divisors
</pre>
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