A146053 Number of n X n binary arrays symmetric under 180 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, 5, 29, 139, 901, 5485, 74291, 1056181, 24810777, 651071773, 25748617719, 1169149922235, 81072042123257, 6590052771959131

Offset

1,4

Links

Table of n, a(n) for n=1..16.

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: A034332 A273027 A268957 * A163082 A189430 A273078

Adjacent sequences: A146050 A146051 A146052 * A146054 A146055 A146056

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved