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A145807 1/2 the number of islands of ones fitting in an n X n array symmetric under 180 degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally. 0
0, 0, 1, 2, 3, 4, 6, 8, 9, 12, 14, 18, 20, 23, 27, 32 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..16.

EXAMPLE

8 X 8 example with 16 islands

.0.1.0.1.0.1.0.1

.0.1.0.1.0.1.0.1

.1.0.1.0.1.0.1.0

.1.0.1.0.1.0.1.0

.0.1.0.1.0.1.0.1

.0.1.0.1.0.1.0.1

.1.0.1.0.1.0.1.0

.1.0.1.0.1.0.1.0

CROSSREFS

Sequence in context: A113961 A116621 A036407 * A278962 A122380 A033501

Adjacent sequences:  A145804 A145805 A145806 * A145808 A145809 A145810

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 19 2008

STATUS

approved

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Last modified November 19 00:12 EST 2018. Contains 317332 sequences. (Running on oeis4.)