A146035 Number of n X n binary arrays symmetric about the diagonal and under 90 degree rotation with all ones connected only in a 3X3 el 1,1 1,2 1,3 2,3 3,3 in any orientation.

1, 1, 1, 1, 1, 1, 3, 3, 7, 7, 15, 15, 39, 39, 189, 189, 995, 995, 5569, 5569, 37913, 37913, 366061, 366061, 4244909, 4244909, 58320195, 58320195, 974389263, 974389263

Offset

1,7

Links

Table of n, a(n) for n=1..30.

Example

Maximal 8 X 8 example
.0.0.1.0.0.1.0.0
.0.0.1.0.0.1.0.0
.1.1.1.0.0.1.1.1
.0.0.0.0.0.0.0.0
.0.0.0.0.0.0.0.0
.1.1.1.0.0.1.1.1
.0.0.1.0.0.1.0.0
.0.0.1.0.0.1.0.0

Crossrefs

Sequence in context: A147252 A147104 A147381 * A147190 A146450 A233810

Adjacent sequences: A146032 A146033 A146034 * A146036 A146037 A146038

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved