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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Table of n, a(n) for n=1..20.

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: A144367 A075465 A011868 * A240865 A039859 A130291

Adjacent sequences:  A145810 A145811 A145812 * A145814 A145815 A145816

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 20 2008

STATUS

approved

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Last modified October 22 12:22 EDT 2018. Contains 316446 sequences. (Running on oeis4.)