$\displaystyle \frac{1}{15}$\displaystyle \frac{1}{15}

$\displaystyle \frac{2}{27}$\displaystyle \frac{2}{27}

$\displaystyle \frac{4}{81}$\displaystyle \frac{4}{81}

$\displaystyle \frac{8}{243}$\displaystyle \frac{8}{243}