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

1,4

LINKS

Table of n, a(n) for n=1..22.

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: A156287 A162293 A233459 * A018629 A018357 A061489

Adjacent sequences:  A145800 A145801 A145802 * A145804 A145805 A145806

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 19 2008

STATUS

approved

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Last modified July 13 05:18 EDT 2020. Contains 335673 sequences. (Running on oeis4.)