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, 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

Table of n, a(n) for n=1..7.

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

Cf. A108798, A102894, A193674, A102896.

Sequence in context: A113094 A327128 A320669 * A076113 A182335 A362288

Adjacent sequences: A299113 A299114 A299115 * A299117 A299118 A299119

Keyword

nonn,more

Author

Gunnar Brinkmann, Feb 05 2018

Status

approved