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A145937 Number of n X n binary arrays symmetric under horizontal and vertical reflection with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation. 0
1, 1, 1, 1, 5, 5, 19, 19, 161, 161, 4227, 4227, 156459, 156459, 12465353, 12465353, 2072728127, 2072728127, 654619864141, 654619864141, 416229285287827, 416229285287827, 526917547596105835, 526917547596105835 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Table of n, a(n) for n=1..24.

FORMULA

Maximal 8 X 8 example

.1.1.0.0.0.0.1.1

.1.0.1.0.0.1.0.1

.0.1.1.0.0.1.1.0

.0.0.0.0.0.0.0.0

.0.0.0.0.0.0.0.0

.0.1.1.0.0.1.1.0

.1.0.1.0.0.1.0.1

.1.1.0.0.0.0.1.1

CROSSREFS

Sequence in context: A147101 A147141 A146146 * A246983 A305514 A039914

Adjacent sequences:  A145934 A145935 A145936 * A145938 A145939 A145940

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved

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Last modified July 30 07:41 EDT 2021. Contains 346348 sequences. (Running on oeis4.)