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A145803
1/2 the number of islands of ones fitting in an n X n array symmetric under horizontal and vertical reflection with all ones connected only either two adjacent vertically or two adjacent horizontally.
0
0, 0, 0, 2, 3, 4, 6, 7, 9, 12, 14, 16, 20, 23, 25, 30, 34, 38, 42, 46, 53, 58
OFFSET
1,4
EXAMPLE
8 X 8 example with 14 islands
.1.1.0.1.1.0.1.1
.0.0.0.0.0.0.0.0
.1.1.0.1.1.0.1.1
.0.0.1.0.0.1.0.0
.0.0.1.0.0.1.0.0
.1.1.0.1.1.0.1.1
.0.0.0.0.0.0.0.0
.1.1.0.1.1.0.1.1
CROSSREFS
Sequence in context: A374484 A162293 A233459 * A018629 A018357 A061489
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 19 2008
STATUS
approved