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A146051 Number of n X n binary arrays symmetric about the diagonal and under 90 degree rotation with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation. 0
1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 13, 13, 35, 35, 181, 181, 1303, 1303, 13131, 13131, 161693, 161693, 2592581, 2592581, 57377381, 57377381, 1720164275, 1720164275 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

Maximal 9 X 9 example

.0.0.1.1.0.1.1.0.0

.0.0.1.1.0.1.1.0.0

.1.1.0.1.0.1.0.1.1

.1.1.1.0.0.0.1.1.1

.0.0.0.0.0.0.0.0.0

.1.1.1.0.0.0.1.1.1

.1.1.0.1.0.1.0.1.1

.0.0.1.1.0.1.1.0.0

.0.0.1.1.0.1.1.0.0

CROSSREFS

Sequence in context: A146193 A146727 A146426 * A146229 A146020 A145948

Adjacent sequences:  A146048 A146049 A146050 * A146052 A146053 A146054

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 26 2008

STATUS

approved

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Last modified January 16 05:22 EST 2022. Contains 350374 sequences. (Running on oeis4.)