A145939 - OEIS

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A145939

Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation.

1, 1, 3, 5, 15, 39, 133, 511, 2773, 14873, 106373, 810293, 8275081, 88902809, 1280398135, 19384764865, 392921704943, 8381650583597, 239524090999801, 7208159770278487, 290528855860261289, 12317566856380616673

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

OFFSET

1,3

LINKS

Table of n, a(n) for n=1..22.

EXAMPLE

Maximal 8 X 8 example

.0.1.1.0.1.0.1.1

.1.0.1.0.1.1.0.1

.1.1.0.1.0.0.1.0

.0.0.1.1.0.0.1.1

.1.1.0.0.1.1.0.0

.0.1.0.0.1.0.1.1

.1.0.1.1.0.1.0.1

.1.1.0.1.0.1.1.0

CROSSREFS

Sequence in context: A280764 A148503 A236571 * A161703 A018551 A103425

Adjacent sequences: A145936 A145937 A145938 * A145940 A145941 A145942

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved