A145937 Number of n X n binary arrays symmetric under horizontal and vertical reflection with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation.

1, 1, 1, 1, 5, 5, 19, 19, 161, 161, 4227, 4227, 156459, 156459, 12465353, 12465353, 2072728127, 2072728127, 654619864141, 654619864141, 416229285287827, 416229285287827, 526917547596105835, 526917547596105835

Offset

1,5

Links

Table of n, a(n) for n=1..24.

Formula

Maximal 8 X 8 example

.1.1.0.0.0.0.1.1

.1.0.1.0.0.1.0.1

.0.1.1.0.0.1.1.0

.0.0.0.0.0.0.0.0

.0.0.0.0.0.0.0.0

.0.1.1.0.0.1.1.0

.1.0.1.0.0.1.0.1

.1.1.0.0.0.0.1.1

Crossrefs

Sequence in context: A147101 A147141 A146146 * A246983 A305514 A039914

Adjacent sequences: A145934 A145935 A145936 * A145938 A145939 A145940

Keyword

nonn

Author

R. H. Hardin, Oct 25 2008

Status

approved