S_{n} = \frac{8}{n^{2}} \cdot \frac{n (n - 1)}{2} = 4 \frac{n - 1}{n} = 4 - \frac{4}{n}

${S_n = \frac {8} {n^2} \cdot \frac {n(n - 1)} {2} = 4 \frac {n - 1} {n} = 4 - \frac {4} {n}}$

Error