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A145806
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1/4 of the number of islands of ones fitting in an n X n array symmetric under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.
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0
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0, 0, 0, 1, 1, 2, 3, 3, 4, 6, 6, 8, 10, 11, 12, 15, 16, 18, 21, 23, 25
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,6
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LINKS
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EXAMPLE
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8 X 8 example with 12 islands:
0 0 0 1 0 0 1 0
1 1 0 1 0 0 1 0
0 0 1 0 1 1 0 0
0 0 1 0 0 0 1 1
1 1 0 0 0 1 0 0
0 0 1 1 0 1 0 0
0 1 0 0 1 0 1 1
0 1 0 0 1 0 0 0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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