login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A145942
Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation.
0
1, 1, 3, 13, 59, 335, 2897, 37715, 690357, 17737939, 624778919, 31083795113, 2181813132547, 218875670124419, 30699194550031869, 6100362669555259551, 1691513945329277743047, 667365921802550365450107
OFFSET
1,3
EXAMPLE
Maximal 8 X 8 example
.1.0.0.1.1.0.1.1
.1.1.0.0.1.0.0.1
.0.0.1.1.0.1.1.0
.1.1.0.1.0.1.0.1
.1.0.1.0.1.0.1.1
.0.1.1.0.1.1.0.0
.1.0.0.1.0.0.1.1
.1.1.0.1.1.0.0.1
CROSSREFS
Sequence in context: A330799 A367057 A317776 * A331517 A340411 A074437
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 25 2008
STATUS
approved