A145942 Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation.

1, 1, 3, 13, 59, 335, 2897, 37715, 690357, 17737939, 624778919, 31083795113, 2181813132547, 218875670124419, 30699194550031869, 6100362669555259551, 1691513945329277743047, 667365921802550365450107

Offset

1,3

Links

Table of n, a(n) for n=1..18.

Example

Maximal 8 X 8 example
.1.0.0.1.1.0.1.1
.1.1.0.0.1.0.0.1
.0.0.1.1.0.1.1.0
.1.1.0.1.0.1.0.1
.1.0.1.0.1.0.1.1
.0.1.1.0.1.1.0.0
.1.0.0.1.0.0.1.1
.1.1.0.1.1.0.0.1

Crossrefs

Sequence in context: A330799 A367057 A317776 * A331517 A340411 A074437

Adjacent sequences: A145939 A145940 A145941 * A145943 A145944 A145945

Keyword

nonn

Author

R. H. Hardin, Oct 25 2008

Status

approved