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Search: id:A145816
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| A145816 |
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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 three adjacent vertically or three adjacent horizontally. |
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+0
1
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| 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 5, 6, 7, 9, 9, 11, 12, 14, 15, 17, 18
(list; graph; listen)
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OFFSET
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1,7
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EXAMPLE
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8 X 8 example with 8 islands
.1.0.0.1.0.1.1.1
.1.0.0.1.0.0.0.0
.1.0.0.1.0.0.0.0
.0.0.0.0.0.1.1.1
.1.1.1.0.0.0.0.0
.0.0.0.0.1.0.0.1
.0.0.0.0.1.0.0.1
.1.1.1.0.1.0.0.1
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CROSSREFS
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Sequence in context: A143752 A145933 A120171 this_sequence A027583 A029022 A140953
Adjacent sequences: A145813 A145814 A145815 this_sequence A145817 A145818 A145819
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KEYWORD
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nonn
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AUTHOR
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Ron Hardin (rhhardin(AT)att.net), Oct 20 2008
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