if ( strlen($n) == 0 )
{
echo "No number was input.<br/>";
echo "Come <a href=\"javascript:history.back(1);\">back</a> to the form and retry." ;
return ;
}
$pf = new primesfactory ;
$pf->insert_number( $n );
$pf->go();
if ( !$pf->isok() ) $pf->display_error();
else
{
echo "<b>The sieve of Eratosthenes</b><br/><br/><font color=#EEEE00><b>Primes</b></font> before <b>$n</b> are:<br/><br/>" ;