A146051 Number of n X n binary arrays symmetric about the diagonal and under 90 degree rotation with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.

1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 13, 13, 35, 35, 181, 181, 1303, 1303, 13131, 13131, 161693, 161693, 2592581, 2592581, 57377381, 57377381, 1720164275, 1720164275

Offset

1,9

Links

Table of n, a(n) for n=1..28.

Example

Maximal 9 X 9 example
.0.0.1.1.0.1.1.0.0
.0.0.1.1.0.1.1.0.0
.1.1.0.1.0.1.0.1.1
.1.1.1.0.0.0.1.1.1
.0.0.0.0.0.0.0.0.0
.1.1.1.0.0.0.1.1.1
.1.1.0.1.0.1.0.1.1
.0.0.1.1.0.1.1.0.0
.0.0.1.1.0.1.1.0.0

Crossrefs

Sequence in context: A146193 A146727 A146426 * A146229 A146020 A145948

Adjacent sequences: A146048 A146049 A146050 * A146052 A146053 A146054

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved