%I
%S 2,2,6,58,3770
%N Number of unlabeled T_0 sets of subsets of {1..n} that cover all n vertices.
%C 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},{2,3}} is {{1},{1,2},{2}}. The T_0 condition means that the dual is strict (no repeated edges).
%F a(n) = 2 * A319637(n).
%e Nonisomorphic representatives of the a(0) = 2 through a(2) = 6 sets of subsets:
%e {} {{1}} {{1},{2}}
%e {{}} {{},{1}} {{2},{1,2}}
%e {{},{1},{2}}
%e {{},{2},{1,2}}
%e {{1},{2},{1,2}}
%e {{},{1},{2},{1,2}}
%Y The nonT_0 version is A003181.
%Y The case without empty edges is A319637.
%Y The labeled version is A326939.
%Y The noncovering version is A326949 (partial sums).
%Y Cf. A000371, A003180, A055621, A059201, A316978, A319559, A319564, A326907, A326941, A326943, A326946.
%K nonn,more
%O 0,1
%A _Gus Wiseman_, Aug 07 2019
