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A145814 1/4 of the number of islands of ones fitting in an n X n array symmetric about both diagonal and antidiagonal with all ones connected only either three adjacent vertically or three adjacent horizontally. 0
0, 0, 0, 0, 1, 1, 1, 1, 3, 3, 4, 4, 6, 6, 7, 8, 10, 11, 12, 13, 15, 16, 19, 20, 22 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

8 X 8 example with 4 islands

.0.0.0.0.1.0.0.0

.0.0.0.0.1.0.0.0

.0.0.0.0.1.0.0.0

.0.0.0.0.0.1.1.1

.1.1.1.0.0.0.0.0

.0.0.0.1.0.0.0.0

.0.0.0.1.0.0.0.0

.0.0.0.1.0.0.0.0

CROSSREFS

Sequence in context: A108942 A025561 A187321 * A198465 A240116 A007768

Adjacent sequences:  A145811 A145812 A145813 * A145815 A145816 A145817

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 20 2008

STATUS

approved

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Last modified August 28 09:24 EDT 2014. Contains 246166 sequences.