1、$\sum_{i=1}^n {2i-1} = i^2$

2、$\sum_{i=1}^n {i(i+1)} =\frac {n(n+1)(n+2)}{3}$

3、$\sum_{i=1}^n {i^2(i-1)!} = (n+1)!+1$

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

5、$\sum_{i=1}^n {i^3} = (\frac{i(i+1)}{2})^2$