Erdős-primes: Difference between revisions

=={{header|Perl}}==

{{libheader|ntheory}}

<lang perl>use strict;

use warnings;

use feature 'say';

use utf8;

binmode(STDOUT, ':utf8');

use List::AllUtils 'before';

use ntheory qw<is_prime factorial>;

sub is_erdos {

my($n) = @_; my $k;

return unless is_prime($n);

while ($n > factorial($k++)) { return if is_prime $n-factorial($k) }

'True'

}

my(@Erdős,$n);

do { push @Erdős, $n if is_erdos(++$n) } until $n >= 1e6;

say 'Erdős primes < ' . (my $max = 2500) . ':';

say join ' ', before { $_ > 2500 } @Erdős;

say "\nErdős prime #" . @Erdős . ' is ' . $Erdős[-1];</lang>

{{out}}

<pre>Erdős primes < 2500:

2 101 211 367 409 419 461 557 673 709 769 937 967 1009 1201 1259 1709 1831 1889 2141 2221 2309 2351 2411 2437

Erdős prime #7875 is 999721</pre>