设集合X={}a1,a2,a3,,an,f(n,m)表示X的含m个元素的不同封闭集族的数目.证明了f(n,6)=7n-7/2·6n+5n+1-4n+1+2·3n-2n-1,其中n=1,2,3,….
Let set X={a 1,a 2,a3,,an},the number of closed family of sets with m elements is denoted by f(n,m).In this paper,we prove that:f(n,6)=7n-7/2·6n+5n+1-4n+1+2·3n-2n-1,in which n=1,2,3,….