A140217 Half the number of n X n binary matrices, symmetric under horizontal reflection, having equal row sums.

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

Adjacent sequences: A140214 A140215 A140216 * A140218 A140219 A140220

Keyword

nonn

Author

R. H. Hardin, Jul 28 2008

Status

approved