A145861 Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in two by two blocks.

1, 2, 1, 4, 4, 13, 13, 58, 68, 386, 540, 3520, 6019, 47375, 94643, 905453, 2187052, 24871767, 71992142, 980875049, 3393779522, 55564082030, 230467066626, 4514573141799, 22448445351838, 526789383889476, 3136759423470421

Offset

1,2

Links

Table of n, a(n) for n=1..27.

Example

Maximal 7 X 7 example
.1.1.0.1.1.0.0
.1.1.0.1.1.0.0
.0.0.0.0.0.1.1
.1.1.0.0.0.1.1
.1.1.0.0.0.0.0
.0.0.1.1.0.1.1
.0.0.1.1.0.1.1

Crossrefs

Sequence in context: A048049 A212716 A057772 * A191660 A129874 A021983

Adjacent sequences: A145858 A145859 A145860 * A145862 A145863 A145864

Keyword

nonn

Author

R. H. Hardin, Oct 22 2008

Status

approved