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Number of unlabeled antichains of finite sets spanning up to n vertices with singleton edges allowed.
10

%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