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A145814
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1/4 of the number of islands of ones fitting in an n X n array symmetric about both diagonal and antidiagonal with all ones connected only either three adjacent vertically or three adjacent horizontally.
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0
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0, 0, 0, 0, 1, 1, 1, 1, 3, 3, 4, 4, 6, 6, 7, 8, 10, 11, 12, 13, 15, 16, 19, 20, 22
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,9
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LINKS
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EXAMPLE
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8 X 8 example with 4 islands
.0.0.0.0.1.0.0.0
.0.0.0.0.1.0.0.0
.0.0.0.0.1.0.0.0
.0.0.0.0.0.1.1.1
.1.1.1.0.0.0.0.0
.0.0.0.1.0.0.0.0
.0.0.0.1.0.0.0.0
.0.0.0.1.0.0.0.0
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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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