摘要：
(2018中科大自招)
设$S=\{1,2,3,4,5\}$则满足$f(f(x))=x$的映射:$S \longrightarrow S$的个数____ 阅读全文
摘要：
(2018中科大自招最后一题)
设$a_1=1,a_{n+1}=\left(1+\dfrac{1}{n}\right)^3(n+a_n)$证明:
(1)$a_n=n^3\left(1+\sum\limits_{k=1}^{n-1}\dfrac{1}{k^2}\right);
(2)\prod\limits_{k=1}^n\left(1+\dfrac{k}{a_k}\right)<3$ 阅读全文