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A323820
Number of non-isomorphic connected set-systems covering n vertices with no singletons.
1
1, 0, 1, 6, 171, 611846, 200253853704319, 263735716028826427334553304608242, 5609038300883759793482640992086670066496449147691597380632107520565546
OFFSET
0,4
COMMENTS
The labeled case is A323817.
FORMULA
Inverse Euler transform of A317795.
EXAMPLE
Non-isomorphic representatives of the a(3) = 6 set-systems:
{{1,2,3}}
{{1,3},{2,3}}
{{2,3},{1,2,3}}
{{1,2},{1,3},{2,3}}
{{1,3},{2,3},{1,2,3}}
{{1,2},{1,3},{2,3},{1,2,3}}
CROSSREFS
Cf. A000295, A003465, A016031, A048143, A055621, A293510, A305001, A317795 (not necessarily connected), A323817 (unlabeled case), A323819 (with singletons).
Sequence in context: A264796 A266852 A266311 * A317795 A166762 A323279
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 30 2019
STATUS
approved