[数论]数论中重要公式[整理]

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