%I #12 Aug 14 2019 16:45:12
%S 1,2,6,24,166,3266,826308
%N Number of unlabeled antichains of finite sets spanning up to n vertices with singleton edges allowed.
%e Non-isomorphic representatives of the a(3) = 24 antichains:
%e {}
%e {{1}}
%e {{1,2}}
%e {{1,2,3}}
%e {{1},{2}}
%e {{2},{1,2}}
%e {{3},{1,2}}
%e {{3},{1,2,3}}
%e {{1,3},{2,3}}
%e {{1},{2},{3}}
%e {{1},{2},{1,2}}
%e {{2},{3},{1,3}}
%e {{2},{3},{1,2,3}}
%e {{3},{1,2},{2,3}}
%e {{3},{1,3},{2,3}}
%e {{1,2},{1,3},{2,3}}
%e {{1},{2},{3},{2,3}}
%e {{1},{2},{3},{1,2,3}}
%e {{2},{3},{1,2},{1,3}}
%e {{2},{3},{1,3},{2,3}}
%e {{3},{1,2},{1,3},{2,3}}
%e {{1},{2},{3},{1,3},{2,3}}
%e {{2},{3},{1,2},{1,3},{2,3}}
%e {{1},{2},{3},{1,2},{1,3},{2,3}}
%Y Partial sums of A304997.
%Y Cf. A006126, A261005, A304997, A304998, A304999, A305000, A305001.
%Y Cf. A000372, A014466, A293993, A319639, A319721, A326704, A326972.
%K nonn,more
%O 0,2
%A _Gus Wiseman_, May 23 2018
%E a(5)-a(6) from _Andrew Howroyd_, Aug 14 2019