long factor = 20L;
int max = 0;
for (long i = 20L; i 10; j–) {
if (i % j != 0)
break;
else {
if (factor % j != 0) {
factor = i;
max++;
}
}

if (j == 11) {
System.out.println(i);
System.exit(0);
}
}
}

my( @primes, %powers );
for ( $i = 2; $i <= 20; $i++ )
{
my $prime = 1;
$j = $i;
foreach my $x ( @primes )
{
my $power = 0;
while ( ( $j % $x ) == 0 )
{
$power++;
$j /= $x;
$prime = 0;
}
if ( $power > $powers{ $x } )
{
$powers{ $x } = $power;
}
}
if ( $prime )
{
push( @primes, $i );
$powers{ $i } = 1;
}
}
my $out = 1;
foreach my $x ( @primes )
{
$out *= ( $x ** $powers{ $x } );
}
print $out;

my( @primes, %factors );
for ( $i = 2; $i $factors{ $x } )
{
$factors{ $x } = $power;
}
}
if ( $prime )
{
push( @primes, $i );
$factors{ $i } = 1;
}
}
my $out = 1;
foreach my $x ( @primes )
{
$out *= ( $x ** $factors{ $x } );
}
print $out;
// or, if you prefer, die $out;

This works in a fraction of the time of the second script given in the post. And it works in nearly the same time for much higher upper limits, too: if you try changing the upper limit from 20 to 30, the iterative method takes a long, long time, while looking for prime factors is still practically instantaneous. In fact, the iterative method will stop working entirely when the result is beyond the limit of the integer math of the language, while the factor-finding method will still at least have the right factors, and (in Perl) will still print the result in scientific notation — the lowest common multiple of the first 200 integers is approximately 3.37293588832926e+89.