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A309667 Number of non-isomorphic connected set-systems on up to n vertices.

%I A309667 #9 Aug 14 2019 19:15:50
%S A309667 1,2,5,35,1947,18664537,12813206150464222,
%T A309667 33758171486592987151274638818642016,
%U A309667 1435913805026242504952006868879460423801146743462225386062178112354069599
%N A309667 Number of non-isomorphic connected set-systems on up to n vertices.
%C A309667 A set-system is a finite set of finite nonempty sets.
%H A309667 Alois P. Heinz, <a href="/A309667/b309667.txt">Table of n, a(n) for n = 0..12</a>
%e A309667 Non-isomorphic representatives of the a(0) = 1 through a(2) = 5 set-systems:
%e A309667   {}  {}     {}
%e A309667       {{1}}  {{1}}
%e A309667              {{1,2}}
%e A309667              {{2},{1,2}}
%e A309667              {{1},{2},{1,2}}
%Y A309667 The covering case is A323819 (first differences).
%Y A309667 The BII-numbers of connected set-systems are A326749.
%Y A309667 The labeled version is A326964.
%Y A309667 Cf. A000371, A000612, A001187, A007718, A058891, A092918, A261006, A300913, A323818.
%K A309667 nonn
%O A309667 0,2
%A A309667 _Gus Wiseman_, Aug 11 2019