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A299116
The number of sparse union-closed sets. That is, the number of union-closed sets on n elements containing the empty set and the universe, such that in average each set (not counting the empty set) has at most n/2 elements.
0
0, 0, 0, 2, 27, 3133, 5777931
OFFSET
1,4
COMMENTS
If there is a counterexample to the union-closed set conjecture, it is a sparse union-closed set.
LINKS
G. Brinkmann and R. Deklerck, Generation of Union-Closed Sets and Moore Families, arXiv:1701.03751 [math.CO], 2017.
G. Brinkmann and R. Deklerck, Generation of Union-Closed Sets and Moore Families, Journal of Integer Sequences, Vol.21 (2018), Article 18.1.7.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gunnar Brinkmann, Feb 05 2018
STATUS
approved