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 A319640 #6 Oct 26 2018 12:50:18
%S A319640 1,1,1,2,7,70
%N A319640 Number of non-isomorphic antichain covers of n vertices by distinct sets whose dual is also an antichain of distinct sets.
%C A319640 The dual of a multiset partition has, for each vertex, one block consisting of the indices (or positions) of the blocks containing that vertex, counted with multiplicity. For example, the dual of {{1,2},{2,2}} is {{1},{1,2,2}}.
%e A319640 Non-isomorphic representatives of the a(1) = 1 through a(4) = 7 antichains:
%e A319640 1: {{1}}
%e A319640 2: {{1},{2}}
%e A319640 3: {{1},{2},{3}}
%e A319640 {{1,2},{1,3},{2,3}}
%e A319640 4: {{1},{2},{3},{4}}
%e A319640 {{1},{2,3},{2,4},{3,4}}
%e A319640 {{1,2},{1,3},{1,4},{2,3,4}}
%e A319640 {{1,2},{1,3},{2,4},{3,4}}
%e A319640 {{1,2,3},{1,2,4},{1,3,4},{2,3,4}}
%e A319640 {{1,3},{1,4},{2,3},{2,4},{3,4}}
%e A319640 {{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}}
%Y A319640 Cf. A006126, A007716, A049311, A059201, A283877, A293606, A316980, A316983, A318099, A319558, A319616-A319646, A300913.
%K A319640 nonn,more
%O A319640 0,4
%A A319640 _Gus Wiseman_, Sep 25 2018