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Proper divisors: Difference between revisions
PHP
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79 divisors:{15120,18480}
</pre>
=={{header|PHP}}==
<lang php><?php
function ProperDivisors($n) {
yield 1;
$large_divisors = [];
for ($i = 2; $i <= sqrt($n); $i++) {
if ($n % $i == 0) {
yield $i;
if ($i*$i != $n) {
$large_divisors[] = $n / $i;
}
}
}
foreach (array_reverse($large_divisors) as $i) {
yield $i;
}
}
assert([1, 2, 4, 5, 10, 20, 25, 50] ==
iterator_to_array(ProperDivisors(100)));
foreach (range(1, 10) as $n) {
echo "$n =>";
foreach (ProperDivisors($n) as $divisor) {
echo " $divisor";
}
echo "\n";
}
$divisorsCount = [];
for ($i = 1; $i < 20000; $i++) {
$divisorsCount[sizeof(iterator_to_array(ProperDivisors($i)))][] = $i;
}
ksort($divisorsCount);
echo "Numbers with most divisors: ", implode(", ", end($divisorsCount)), ".\n";
echo "They have ", key($divisorsCount), " divisors.\n";
</lang>
Outputs:
<pre>1 => 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
Numbers with most divisors: 15120, 18480.
They have 79 divisors.</pre>
=={{header|PicoLisp}}==
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