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A146047 Number of n X n binary arrays symmetric under horizontal reflection 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, 13, 19, 471, 1011, 17363, 51133, 4227773, 17426251, 4189737457, 23548416611, 8347118368027, 61971666176727, 58964882823496375, 583865226098623749, 1588500435723596374221, 21184137467738936180415 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

Maximal 8 X 8 example

.1.1.0.0.0.0.1.1

.1.1.0.0.0.0.1.1

.1.0.0.0.0.0.0.1

.0.1.1.0.0.1.1.0

.0.1.1.0.0.1.1.0

.0.0.1.0.0.1.0.0

.1.1.0.0.0.0.1.1

.1.1.1.0.0.1.1.1

CROSSREFS

Sequence in context: A166664 A147393 A088187 * A343034 A145944 A355964

Adjacent sequences: A146044 A146045 A146046 * A146048 A146049 A146050

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 26 2008

STATUS

approved

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Last modified March 28 19:22 EDT 2023. Contains 361596 sequences. (Running on oeis4.)