my @one = qw( 1 3 5 7 9 11 13 13 15 15 17 19 21 23 );
my @two = qw( 1   5   9    13          17    21    );

my %valid; 

$valid{$_}++ for @one; 
@valid{@two} = (0) x @two; 

@choices = map { ($_) x $valid{$_} } keys %valid;

sub randelt { $choices[rand @choices] }