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A145942 Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation. 0
1, 1, 3, 13, 59, 335, 2897, 37715, 690357, 17737939, 624778919, 31083795113, 2181813132547, 218875670124419, 30699194550031869, 6100362669555259551, 1691513945329277743047, 667365921802550365450107 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

EXAMPLE

Maximal 8 X 8 example

.1.0.0.1.1.0.1.1

.1.1.0.0.1.0.0.1

.0.0.1.1.0.1.1.0

.1.1.0.1.0.1.0.1

.1.0.1.0.1.0.1.1

.0.1.1.0.1.1.0.0

.1.0.0.1.0.0.1.1

.1.1.0.1.1.0.0.1

CROSSREFS

Sequence in context: A151233 A151234 A317776 * A074437 A026578 A199641

Adjacent sequences:  A145939 A145940 A145941 * A145943 A145944 A145945

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved

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Last modified May 27 02:54 EDT 2019. Contains 323597 sequences. (Running on oeis4.)