This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A304996 #12 Aug 14 2019 16:45:12
%S A304996 1,2,6,24,166,3266,826308
%N A304996 Number of unlabeled antichains of finite sets spanning up to n vertices with singleton edges allowed.
%e A304996 Non-isomorphic representatives of the a(3) = 24 antichains:
%e A304996 {}
%e A304996 {{1}}
%e A304996 {{1,2}}
%e A304996 {{1,2,3}}
%e A304996 {{1},{2}}
%e A304996 {{2},{1,2}}
%e A304996 {{3},{1,2}}
%e A304996 {{3},{1,2,3}}
%e A304996 {{1,3},{2,3}}
%e A304996 {{1},{2},{3}}
%e A304996 {{1},{2},{1,2}}
%e A304996 {{2},{3},{1,3}}
%e A304996 {{2},{3},{1,2,3}}
%e A304996 {{3},{1,2},{2,3}}
%e A304996 {{3},{1,3},{2,3}}
%e A304996 {{1,2},{1,3},{2,3}}
%e A304996 {{1},{2},{3},{2,3}}
%e A304996 {{1},{2},{3},{1,2,3}}
%e A304996 {{2},{3},{1,2},{1,3}}
%e A304996 {{2},{3},{1,3},{2,3}}
%e A304996 {{3},{1,2},{1,3},{2,3}}
%e A304996 {{1},{2},{3},{1,3},{2,3}}
%e A304996 {{2},{3},{1,2},{1,3},{2,3}}
%e A304996 {{1},{2},{3},{1,2},{1,3},{2,3}}
%Y A304996 Partial sums of A304997.
%Y A304996 Cf. A006126, A261005, A304997, A304998, A304999, A305000, A305001.
%Y A304996 Cf. A000372, A014466, A293993, A319639, A319721, A326704, A326972.
%K A304996 nonn,more
%O A304996 0,2
%A A304996 _Gus Wiseman_, May 23 2018
%E A304996 a(5)-a(6) from _Andrew Howroyd_, Aug 14 2019