A140984 Half the number of n X n binary matrices, symmetric under 180 degree rotation, having equal row sums.

1, 2, 4, 35, 226, 7592, 156752, 22458249, 1718157826, 941605438142, 250228936146872, 572800408273738658, 580834777459374862880, 5136409738603278958315040, 18792196647668946085817284928

Offset

1,2

Links

R. H. Hardin, Jul 28 2008, Table of n, a(n) for n = 1..25

Crossrefs

Sequence in context: A132529 A027681 A348094 * A057996 A009090 A009295

Adjacent sequences: A140981 A140982 A140983 * A140985 A140986 A140987

Keyword

nonn

Author

R. H. Hardin, Jul 28 2008

Status

approved