A147127 Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 1000-1000-1111-1000 pattern in any orientation.

1, 1, 1, 1, 1, 1, 1, 1, 3, 7, 15, 27, 51, 137, 397, 1327, 4515, 15837, 61007, 262125, 1291801

Offset

1,9

Links

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

Example

Maximal 9 X 9 example
.0.0.0.1.1.1.1.0.0
.0.0.0.0.1.0.0.0.0
.0.0.0.0.1.0.0.0.1
.1.0.0.0.1.0.0.0.1
.1.1.1.1.0.1.1.1.1
.1.0.0.0.1.0.0.0.1
.1.0.0.0.1.0.0.0.0
.0.0.0.0.1.0.0.0.0
.0.0.1.1.1.1.0.0.0

Crossrefs

Sequence in context: A146742 A146425 A147595 * A146726 A146228 A139806

Adjacent sequences: A147124 A147125 A147126 * A147128 A147129 A147130

Keyword

nonn

Author

R. H. Hardin, Nov 04 2008

Status

approved