公式

$\sum_{i=0}^n i^2 = \frac{(n^2 + n)(2n+1)}{6}$
$\sum_{i=0}^n i^2 = \frac{(n^2 + n)(2n+1)}{6}$
$\sum_{i=0}^n i^2 = \frac{(n^2 + n)(2n+1)}{6}$
$\sum_{i=0}^n i^2 = \frac{(n^2 + n)(2n+1)}{6}$
$\sum_{i=0}^n i^2 = \frac{(n^2 + n)(2n+1)}{6}$