A145864 - OEIS

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A145864

Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in two by two blocks.

0

1, 2, 1, 4, 8, 25, 59, 294, 976, 6868, 36894, 351022, 2656603, 36966909, 391525649, 7896337875, 122564741600, 3503953133171, 77993874405982, 3210152559844391, 101979707965980254, 6040428902857902560, 276387013896712513044

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..23.

EXAMPLE

Maximal 7 X 7 example

.1.1.0.1.1.0.0

.1.1.0.1.1.0.0

.0.0.0.0.0.1.1

.1.1.0.0.0.1.1

.1.1.0.0.0.0.0

.0.0.1.1.0.1.1

.0.0.1.1.0.1.1

CROSSREFS

Sequence in context: A319479 A303632 A133267 * A306392 A182739 A359132

Adjacent sequences: A145861 A145862 A145863 * A145865 A145866 A145867

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 22 2008

STATUS

approved