A093440 Number of n X n symmetric binary matrices with each element either the sum mod 2 of its diagonal neighbors or the sum mod 2 of its antidiagonal neighbors.

1, 4, 20, 100, 720, 7920, 156960, 4978909, 162844632, 9658482053, 917891979225, 113051563311936, 21440096665285608, 6394092372716939840, 2723634378368868283440, 1747667851609071536512000, 1691968139075108292667595716, 2420449673384279037966387855492

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..21

Example

Some solutions for 5X5
..0..0..1..1..0....0..0..1..0..0....1..1..1..1..1....0..0..1..1..1
..0..0..0..1..1....0..1..0..1..0....1..1..1..1..0....0..0..1..1..1
..1..0..1..0..1....1..0..1..1..1....1..1..0..0..0....1..1..0..1..0
..1..1..0..1..0....0..1..1..0..1....1..1..0..0..1....1..1..1..0..0
..0..1..1..0..0....0..0..1..1..0....1..0..0..1..0....1..1..0..0..0

Crossrefs

Sequence in context: A105480 A242156 A186369 * A168606 A229135 A226198

Adjacent sequences: A093437 A093438 A093439 * A093441 A093442 A093443

Keyword

nonn

Author

R. H. Hardin, Jun 26 2011

Status

approved