A146052 Number of n X n binary arrays symmetric 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, 13, 33, 59, 183, 775, 3549, 21203, 124205, 885931, 6938155, 65072235, 697161911, 8870657391, 129325569203, 2224950934319, 42682217569275, 961782024725197, 24665663177266467

Offset

1,6

Links

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

Example

Maximal 8 X 8 example
.1.1.0.1.0.1.1.1
.1.1.0.1.1.0.1.1
.1.0.0.1.1.0.0.0
.0.1.1.0.0.1.1.1
.1.1.1.0.0.1.1.0
.0.0.0.1.1.0.0.1
.1.1.0.1.1.0.1.1
.1.1.1.0.1.0.1.1

Crossrefs

Sequence in context: A213686 A050659 A123161 * A082109 A024839 A146177

Adjacent sequences: A146049 A146050 A146051 * A146053 A146054 A146055

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved