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A140217
Half the number of n X n binary matrices, symmetric under horizontal reflection, having equal row sums.
1
1, 1, 2, 9, 34, 730, 4376, 905345, 10601986, 10009765626, 200097656252, 2177748514672962, 85812416258106784, 4142789042980129347156, 289904403212517959978240, 175519033940460517461369847809
OFFSET
1,3
LINKS
R. H. Hardin, Jul 28 2008, Table of n, a(n) for n = 1..25
CROSSREFS
Sequence in context: A276901 A151308 A215943 * A182407 A284550 A200050
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 28 2008
STATUS
approved