oeis。
by Querainy @ 2022-06-10 19:45:21
http://oeis.org/A000166
by 小粉兔 @ 2022-06-10 19:45:49
@[zhiyangfan](/user/137603) 带 $n$ 的项不能提到求和号外面的吧
by 小粉兔 @ 2022-06-10 19:52:09
好，完美的推错了。
by zhiyangfan @ 2022-06-10 19:52:38
错排。
by Velix @ 2022-06-10 19:53:49
一眼全错排
by 鏡音リン @ 2022-06-10 19:59:19
[板子](https://www.luogu.com.cn/problem/P4071) 顺便送您一道经验
by kniFe_ @ 2022-06-13 19:38:41