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A146002

Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only in a 3 X 3 "plus" shape (e.g., consisting of the points at the coordinates (2,1), (2,2), (2,3), (1,2), (3,2)).

1, 1, 2, 1, 2, 1, 5, 2, 9, 3, 28, 6, 76, 13, 295, 41, 1196, 134, 6337, 523, 36933, 2341, 266568, 13112, 2186885, 85330, 21909179, 657274, 253725200, 5867785

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

Maximal 8 X 8 example:

0 1 0 0 0 0 1 0

1 1 1 0 0 1 1 1

0 1 0 0 0 0 1 0

0 0 0 0 0 0 0 0

0 1 0 0 0 0 1 0

1 1 1 0 0 1 1 1

0 1 0 0 0 0 1 0

CROSSREFS

Sequence in context: A201733 A000001 A172133 * A109087 A102048 A318360

Adjacent sequences: A145999 A146000 A146001 * A146003 A146004 A146005

KEYWORD

nonn,more

AUTHOR

R. H. Hardin, Oct 26 2008

STATUS

approved