A145857 Number of n X n binary arrays with all ones connected only in two by two blocks.

1, 2, 5, 12, 72, 513, 4531, 68662, 1429824, 40840428, 1747979822, 106711196102, 9237029528023, 1158315077977449, 208422835867809541, 53674442198900292691, 19878424340459715152560, 10569643478952360023168707

Offset: 1

Author

R. H. Hardin, Oct 22 2008

Keywords

• nonn

Examples

			Maximal 7 X 7 example
.0.0.0.1.1.0.0
.1.1.0.1.1.0.0
.1.1.0.0.0.1.1
.0.0.1.1.0.1.1
.0.0.1.1.0.0.0
.1.1.0.0.0.1.1
.1.1.0.0.0.1.1