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Number of non-isomorphic connected set-systems on up to n vertices.
2

%I #9 Aug 14 2019 19:15:50

%S 1,2,5,35,1947,18664537,12813206150464222,

%T 33758171486592987151274638818642016,

%U 1435913805026242504952006868879460423801146743462225386062178112354069599

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

%C A set-system is a finite set of finite nonempty sets.

%H Alois P. Heinz, <a href="/A309667/b309667.txt">Table of n, a(n) for n = 0..12</a>

%e Non-isomorphic representatives of the a(0) = 1 through a(2) = 5 set-systems:

%e {} {} {}

%e {{1}} {{1}}

%e {{1,2}}

%e {{2},{1,2}}

%e {{1},{2},{1,2}}

%Y The covering case is A323819 (first differences).

%Y The BII-numbers of connected set-systems are A326749.

%Y The labeled version is A326964.

%Y Cf. A000371, A000612, A001187, A007718, A058891, A092918, A261006, A300913, A323818.

%K nonn

%O 0,2

%A _Gus Wiseman_, Aug 11 2019