cp's OEIS Frontend

A323820 Number of non-isomorphic connected set-systems covering n vertices with no singletons.

%I A323820 #5 Jan 31 2019 19:33:34
%S A323820 1,0,1,6,171,611846,200253853704319,263735716028826427334553304608242,
%T A323820 5609038300883759793482640992086670066496449147691597380632107520565546
%N A323820 Number of non-isomorphic connected set-systems covering n vertices with no singletons.
%C A323820 The labeled case is A323817.
%F A323820 Inverse Euler transform of A317795.
%e A323820 Non-isomorphic representatives of the a(3) = 6 set-systems:
%e A323820   {{1,2,3}}
%e A323820   {{1,3},{2,3}}
%e A323820   {{2,3},{1,2,3}}
%e A323820   {{1,2},{1,3},{2,3}}
%e A323820   {{1,3},{2,3},{1,2,3}}
%e A323820   {{1,2},{1,3},{2,3},{1,2,3}}
%Y A323820 Cf. A000295, A003465, A016031, A048143, A055621, A293510, A305001, A317795 (not necessarily connected), A323817 (unlabeled case), A323819 (with singletons).
%K A323820 nonn
%O A323820 0,4
%A A323820 _Gus Wiseman_, Jan 30 2019