Given:  Factors 2, 3, 5
2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, ...
3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ...
5, 10, 15, 20, 25, 30, ...

R = 2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, ...

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;

use constant HEAD =>  0;
use constant TAIL => -1;

my $end = shift || 10;
my @num = @ARGV ? @ARGV : (2, 3, 5);
my $next = merge_multiple( \@num );

print $next->(), "\n" for 1 .. $end;

sub merge_multiple {
    my $list = shift;
    return () if ! $list || ref $list ne 'ARRAY';

    my $n = 1;
    my $h = $list->[TAIL];
    my (@pool, @stream);

    return sub {
        return shift @pool if @pool;

        for ( 0 .. $#$list ) {
            my $mult = $list->[ $_ ];
            my $beg = $h * ($n - 1) / $mult + 1;
            my $end = $h * $n / $mult;
            $stream[ $_ ] = [ map { $mult * $_ } $beg .. $end ];
        }
        ++$n;

        @pool = merge( \@stream );
        return shift @pool;
    }
}

sub merge {
    my $stream = shift;
    my $end = $#$stream;

    my @merged;
    while ( 1 ) {
        my $low;
        for ( 0 .. $end ) {
            my $val = $stream->[ $_ ][HEAD];
            next if ! defined $val;
            $low = $_ if ! defined $low || $val < $stream->[ $low ][HEAD];
        }
        last if ! defined $low;
        my $num = shift @{ $stream->[ $low ] };
        next if defined $merged[ TAIL ] && $merged[ TAIL ] == $num;
        push @merged, $num;
    }
    return @merged;
}