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A146049
Number of n X n binary arrays symmetric about main diagonal with all 1's connected only in a 2 X 2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.
0
1, 1, 1, 3, 13, 35, 181, 1303, 13131, 161693, 2592581, 57377381, 1720164275, 69927099465, 3715147371129, 261988046119405, 24980387570081613, 3210146525819915095, 550205755804555982181, 125514016677735094761717
OFFSET
1,4
EXAMPLE
Maximal 8 X 8 example
.0.0.0.0.0.0.1.1
.0.0.0.0.0.0.1.1
.0.0.0.1.1.1.0.1
.0.0.1.0.1.1.0.0
.0.0.1.1.0.0.1.1
.0.0.1.1.0.0.1.1
.1.1.0.0.1.1.0.1
.1.1.1.0.1.1.1.0
CROSSREFS
Sequence in context: A146741 A146725 A146424 * A061483 A340410 A128288
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 26 2008
STATUS
approved