数列基础
等差数列前n项和:\(\frac{1}{2}(a_1+a_n)\)
等比数列的前n项和:\(a_0\times \frac{q^n-1}{q-1}\)
\(\sum_{k=1}^n k^2 = \frac{n(n+1)(2n+1)}{6}\)
\(\sum_{k=1}^n \frac{1}{k(k+1)} = \frac{n}{n+1}\)
等差数列前n项和:\(\frac{1}{2}(a_1+a_n)\)
等比数列的前n项和:\(a_0\times \frac{q^n-1}{q-1}\)
\(\sum_{k=1}^n k^2 = \frac{n(n+1)(2n+1)}{6}\)
\(\sum_{k=1}^n \frac{1}{k(k+1)} = \frac{n}{n+1}\)