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 A319783 #6 Sep 28 2018 15:24:18
%S A319783 1,0,0,1,203,490572
%N A319783 Number of set systems spanning n vertices with empty intersection whose dual is also a set system with empty intersection.
%C A319783 The dual of a multiset partition has, for each vertex, one part consisting of the indices (or positions) of the parts containing that vertex, counted with multiplicity. For example, the dual of {{1,2},{2,2}} is {{1},{1,2,2}}.
%e A319783 The a(3) = 1 set system is {{1,2},{1,3},{2,3}}.
%Y A319783 Cf. A007716, A049311, A281116, A283877, A316980, A317752, A317755, A317757.
%Y A319783 Cf. A319775, A319778, A319779, A319781.
%K A319783 nonn,more
%O A319783 0,5
%A A319783 _Gus Wiseman_, Sep 27 2018