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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

The labeled case is A323817.

LINKS

Table of n, a(n) for n=0..8.

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

Adjacent sequences:  A323817 A323818 A323819 * A323821 A323822 A323823

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 30 2019

STATUS

approved

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Last modified January 26 13:18 EST 2021. Contains 340439 sequences. (Running on oeis4.)