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A145813
1/2 the number of islands of ones fitting in an n X n array symmetric about main diagonal with all ones connected only either three adjacent vertically or three adjacent horizontally.
0
0, 0, 0, 1, 2, 2, 3, 4, 6, 7, 8, 10, 12, 14, 16, 19, 21, 24, 27, 30
OFFSET
1,5
EXAMPLE
8 X 8 example with 8 islands
.0.0.0.0.0.0.0.1
.0.0.0.1.1.1.0.1
.0.0.0.0.0.0.0.1
.0.1.0.0.1.1.1.0
.0.1.0.1.0.0.0.1
.0.1.0.1.0.0.0.1
.0.0.0.1.0.0.0.1
.1.1.1.0.1.1.1.0
CROSSREFS
Sequence in context: A370778 A075465 A011868 * A240865 A039859 A130291
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 20 2008
STATUS
approved