A145864 Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in two by two blocks.

1, 2, 1, 4, 8, 25, 59, 294, 976, 6868, 36894, 351022, 2656603, 36966909, 391525649, 7896337875, 122564741600, 3503953133171, 77993874405982, 3210152559844391, 101979707965980254, 6040428902857902560, 276387013896712513044

Offset

1,2

Links

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

Example

Maximal 7 X 7 example
.1.1.0.1.1.0.0
.1.1.0.1.1.0.0
.0.0.0.0.0.1.1
.1.1.0.0.0.1.1
.1.1.0.0.0.0.0
.0.0.1.1.0.1.1
.0.0.1.1.0.1.1

Crossrefs

Sequence in context: A319479 A303632 A133267 * A306392 A182739 A359132

Adjacent sequences: A145861 A145862 A145863 * A145865 A145866 A145867

Keyword

nonn

Author

R. H. Hardin, Oct 22 2008

Status

approved