A140988 Half the number of symmetric n X n binary matrices having equal row sums.

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

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Crossrefs

Sequence in context: A297630 A297629 A118181 * A136650 A229662 A111885

Adjacent sequences: A140985 A140986 A140987 * A140989 A140990 A140991

Keyword

nonn

Author

R. H. Hardin, Jul 28 2008

Status

approved