本帖最后由 琉璃幻 于 2014-10-15 10:51 编辑
设$G$是个$n$阶群有元素$g_1,g_2,g_3,\cdots g_n$, 且$G$作用于集合$S$
\[G(s)=\{g\circ s|\, s\in S,\forall g\in G \}\]
\[r=\left|\{{t\, |\, G(t_i)\cap G(t_j)=\varnothing}\}\right|\]
\[X(g)=\{s\,|\, g\circ s=s,\, s\in S\}\]
则
\[rn=\sum_{i=1}^{n}\left|X(g_{i})\right|\] |