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A145862
Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only in two by two blocks.
0
1, 2, 1, 2, 2, 5, 3, 12, 6, 32, 16, 104, 49, 441, 169, 2087, 742, 12047, 3848, 83725, 23784, 695140, 176890, 6907583, 1574720, 82485542, 16764539, 1176502867, 214487123, 20130478473
OFFSET
1,2
EXAMPLE
Maximal 7 X 7 example:
0 0 0 0 0 0 0
0 1 1 0 1 1 0
0 1 1 0 1 1 0
0 0 0 0 0 0 0
0 1 1 0 1 1 0
0 1 1 0 1 1 0
0 0 0 0 0 0 0
CROSSREFS
Sequence in context: A128978 A325110 A357888 * A364536 A058701 A004559
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 22 2008
STATUS
approved