A146047 - OEIS

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.

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

.1.0.0.0.0.0.0.1

.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