while ($n != 1) { $result += $cache[$n], last if defined $cache[$n]; $n % 2 ? ( $result += 2, $new_n = (3 * $n + 1) >> 1 ) : ( $result += 1, $new_n = $n >> 1 ); $cache[$n] = $cache[$new_n] + ($n % 2 ? 2 : 1) if defined $cache[$new_n] and $n < $max; $n = $new_n; }