A145931 - OEIS

A145931

Number of n X n binary arrays symmetric under 90-degree rotation with all ones connected only in a T-shape (1,1), (1,2), (1,3), (2,2) in any orientation.

1, 1, 1, 1, 4, 7, 22, 31, 166, 409, 2848, 8224, 74341, 301687, 3626272, 18878730, 299451324, 2103168465, 44919780098, 414592933018, 11582335727655, 142171297585053, 5323365939866750, 86576879487536418, 4274960797178964894

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

OFFSET

1,5

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

Maximal 8 X 8 example:

1 0 0 1 0 1 1 1

1 1 0 1 1 0 1 0

1 0 0 1 0 0 0 0

0 1 0 0 0 1 1 1

1 1 1 0 0 0 1 0

0 0 0 0 1 0 0 1

0 1 0 1 1 0 1 1

1 1 1 0 1 0 0 1

CROSSREFS

Sequence in context: A010363 A119561 A228015 * A026548 A100098 A127361

Adjacent sequences: A145928 A145929 A145930 * A145932 A145933 A145934

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved