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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. +0
1
1, 4, 25, 278, 5532, 200589, 11662671 (list; graph; listen)
OFFSET

1,2

COMMENT

Cover may include multiple occurrences of a subset. Also n-rowed binary matrices with distinct rows and all row sums 4.

LINKS

Formula

CROSSREFS

Cf. A050535, A050913, A058783-A058785.

Sequence in context: A071896 A065740 A144281 this_sequence A093959 A086216 A167041

Adjacent sequences: A058788 A058789 A058790 this_sequence A058792 A058793 A058794

KEYWORD

more,nonn

AUTHOR

Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 30 2000

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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