A140879 Half the number of n X n binary matrices, symmetric about the diagonal and under 90-degree rotation, having equal row sums.

1, 1, 1, 2, 1, 5, 1, 20, 1, 139, 1, 1777, 1, 42295, 1, 1888140, 1, 158903233, 1, 25355226287, 1, 7707419775769, 1

Offset

1,4

Links

Table of n, a(n) for n=1..23.

Crossrefs

Sequence in context: A363739 A257459 A372494 * A006556 A108790 A355914

Adjacent sequences: A140876 A140877 A140878 * A140880 A140881 A140882

Keyword

nonn

Author

R. H. Hardin, Jul 28 2008

Status

approved