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

1,2

Links

Table of n, a(n) for n=1..18.

Example

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

Crossrefs

Sequence in context: A376148 A347598 A293023 * A264863 A197706 A205082

Adjacent sequences: A145854 A145855 A145856 * A145858 A145859 A145860

Keyword

nonn

Author

R. H. Hardin, Oct 22 2008

Status

approved