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

1,4

LINKS

Table of n, a(n) for n=1..18.

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

Adjacent sequences:  A145801 A145802 A145803 * A145805 A145806 A145807

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 19 2008

STATUS

approved

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Last modified June 22 03:55 EDT 2021. Contains 345367 sequences. (Running on oeis4.)