A058791 - OEIS

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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, 4, 25, 278, 5532, 200589, 11662671, 981458725, 111213730857, 16212510876591, 2947663429595884, 653299790376494253, 173373367472722467460, 54295204354760461199529, 19822683467350158062736540

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

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

Table of n, a(n) for n=1..15.

Vladeta Jovovic, Formula

CROSSREFS

Row n=4 of A331508.

Cf. A050535, A050913, A058783, A058784, A058785.

Sequence in context: A144281 A361589 A320569 * A216660 A352859 A374851