S_{n} = \frac{8}{n^{2}} \sum_{i = 1}^{n} i = \frac{8 i}{n^{2}} (1 + 2 + \dots + n + n - 1 + n)

${S_n = \frac {8} {n^2} \sum\limits_{i = 1}^n i = \frac {8i}{n^2} (1 + 2 + \ldots + n + n - 1 + n)}$

Error