摘要: "传送门" 设$f_x$表示答案,那么$f_x = \frac{\sum\limits_{d \mid x} f_d}{\sigma_0(x)} + 1 = \frac{\sigma_0(x) + \sum\limits_{d \mid x , d \neq x} f_d}{\sigma_0(x) 阅读全文
posted @ 2019-07-06 09:30 cjoier_Itst 阅读(301) 评论(1) 推荐(0) 编辑