a(2)=5来自反链{{}}、{{1}},{{2}}和{1,2}},{1}和}}。
a(0)=1到a(3)=19反链:
{{}} {{}} {{}} {{}}
{{1}} {{1}} {{1}}
{{2}} {{2}}
{{12}} {{3}}
{{1}{2}} {{12}}
{{13}}
{{23}}
{{123}}
{{1}{2}}
{{1}{3}}
{{2}{3}}
{{1}{23}}
{{2}{13}}
{{3}{12}}
{{12}{13}}
{{12}{23}}
{{13}{23}}
{{1}{2}{3}}
{{12}{13}{23}}
(结束)
19个集合E使得({1,2,3},E)是一个抽象的简单复数:
{}
{{1}}
{{2}}
{{3}}
{{1}, {2}}
{{1}, {3}}
{{2}, {3}}
{{1}, {2}, {3}}
{{1}, {2}, {1, 2}}
{{1}, {3}, {1, 3}}
{{2}, {3}, {2, 3}}
{{1}, {2}, {3}, {1, 2}}
{{1}, {2}, {3}, {1, 3}}
{{1}, {2}, {3}, {2, 3}}
{{1}, {2}, {3}, {1, 2}, {1, 3}}
{{1}, {2}, {3}, {1, 2}, {2, 3}}
{{1}, {2}, {3}, {1, 3}, {2, 3}}
{{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}}
{{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}}
(结束)