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A058791
Number of covers of an unlabeled n-set such that every point of the set is covered by exactly 4 subsets of the cover and that intersection of every 4 subsets of the cover contains at most one point.
1
1, 4, 25, 278, 5532, 200589, 11662671, 981458725, 111213730857, 16212510876591, 2947663429595884, 653299790376494253, 173373367472722467460, 54295204354760461199529, 19822683467350158062736540
OFFSET
1,2
COMMENTS
Cover may include multiple occurrences of a subset. Also n-rowed binary matrices with distinct rows and all row sums 4.
LINKS
CROSSREFS
Row n=4 of A331508.
Sequence in context: A144281 A361589 A320569 * A216660 A352859 A374851
KEYWORD
more,nonn
AUTHOR
Vladeta Jovovic, Nov 30 2000
EXTENSIONS
a(8)-a(12) from Andrew Howroyd, Jan 29 2020
a(13)-a(15) from Sean A. Irvine, Aug 26 2022
STATUS
approved