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A145804
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 two adjacent vertically or two adjacent horizontally.
0
0, 0, 1, 2, 2, 4, 6, 7, 9, 12, 13, 16, 20, 22, 25, 30, 32, 36
OFFSET
1,4
EXAMPLE
8 X 8 example with 14 islands
.0.1.1.0.0.0.1.1
.1.0.0.1.0.1.0.0
.1.0.0.1.0.1.0.1
.0.1.1.0.0.0.0.1
.0.0.0.0.0.1.1.0
.0.1.1.0.1.0.0.1
.1.0.0.0.1.0.0.1
.1.0.1.1.0.1.1.0
CROSSREFS
Sequence in context: A086536 A053045 A152424 * A227560 A046639 A178702
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 19 2008
STATUS
approved