AC-Evil

摘要： 推导 \(f(c^i)=\sum_{j=0}^{n-1}a_jc^{ij}\) \(ij={i+j\choose 2}-{i\choose 2}-{j\choose 2}\) \[ \begin{aligned} f(c^i)&=\sum_{j=0}^{n-1}a_jc^{{i+j\choose 2 阅读全文