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 A327424 #6 Sep 26 2019 15:24:52
%S A327424 1,1,2,4,10,33,234,16579
%N A327424 Number of unlabeled, non-connected or empty antichains of nonempty subsets of {1..n}.
%C A327424 An antichain is a set of nonempty sets, none of which is a subset of any other. A singleton is considered to be connected.
%e A327424 Non-isomorphic representatives of the a(0) = 1 through a(4) = 10 antichains:
%e A327424 {} {} {} {} {}
%e A327424 {{1},{2}} {{1},{2}} {{1},{2}}
%e A327424 {{1},{2,3}} {{1},{2,3}}
%e A327424 {{1},{2},{3}} {{1},{2},{3}}
%e A327424 {{1},{2,3,4}}
%e A327424 {{1,2},{3,4}}
%e A327424 {{1},{2},{3,4}}
%e A327424 {{1},{2},{3},{4}}
%e A327424 {{1},{2,4},{3,4}}
%e A327424 {{1},{2,3},{2,4},{3,4}}
%Y A327424 Partial sums of the positive-index terms of A327426.
%Y A327424 The covering case is A327426.
%Y A327424 The labeled version is A327354.
%Y A327424 The labeled covering case is A120338.
%Y A327424 Unlabeled antichains that are either not connected or not covering are A327437.
%Y A327424 The case without empty antichains is A327808.
%Y A327424 Cf. A014466, A293606, A326704, A327062, A327355.
%K A327424 nonn,more
%O A327424 0,3
%A A327424 _Gus Wiseman_, Sep 26 2019