MathJax 发表于 2018-03-06 | 更新于: 2018-09-04 变量MATH$\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}$$