A146033 Number of n X n binary arrays symmetric about main diagonal with all ones connected only in a 3X3 el 1,1 1,2 1,3 2,3 3,3 in any orientation.

1, 1, 3, 7, 15, 39, 189, 995, 5569, 37913, 366061, 4244909, 58320195, 974389263, 20855855835, 546928072163, 17575257415665, 693118931384501, 34026835620030291, 2054942936198627105, 152983262052724174217

Offset

1,3

Links

Table of n, a(n) for n=1..21.

Example

Maximal 8 X 8 example
.1.1.1.0.0.1.1.1
.1.0.0.0.0.0.0.1
.1.0.1.1.1.0.0.1
.0.0.1.0.0.0.0.0
.0.0.1.0.1.1.1.0
.1.0.0.0.1.0.0.1
.1.0.0.0.1.0.0.1
.1.1.1.0.0.1.1.1

Crossrefs

Sequence in context: A078161 A216616 A230958 * A147188 A050565 A097111

Adjacent sequences: A146030 A146031 A146032 * A146034 A146035 A146036

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved