先用 Vandermonde 恒等式吧
by 小粉兔 @ 2020-11-27 21:32:24
捕捉兔队
by zplqwq @ 2020-11-27 21:33:59
@[小粉兔](/user/10703) 谢谢
by zhaowangji @ 2020-11-27 21:40:19