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A145939
Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation.
0
1, 1, 3, 5, 15, 39, 133, 511, 2773, 14873, 106373, 810293, 8275081, 88902809, 1280398135, 19384764865, 392921704943, 8381650583597, 239524090999801, 7208159770278487, 290528855860261289, 12317566856380616673
OFFSET
1,3
EXAMPLE
Maximal 8 X 8 example
.0.1.1.0.1.0.1.1
.1.0.1.0.1.1.0.1
.1.1.0.1.0.0.1.0
.0.0.1.1.0.0.1.1
.1.1.0.0.1.1.0.0
.0.1.0.0.1.0.1.1
.1.0.1.1.0.1.0.1
.1.1.0.1.0.1.1.0
CROSSREFS
Sequence in context: A280764 A148503 A236571 * A161703 A018551 A103425
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 25 2008
STATUS
approved