A146050 Number of n X n binary arrays symmetric about both diagonal and antidiagonal 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, 1, 3, 9, 19, 37, 115, 481, 2395, 10969, 57003, 371055, 2992969, 26653005, 266091447, 3019768963, 42043911685, 666291390951, 12240477419651, 251570549673017, 6156133419360705, 172490682719945137

Offset

1,6

Links

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

Example

Maximal 8 X 8 example
.0.0.0.0.1.1.0.0
.0.0.0.0.1.1.0.0
.0.0.0.0.1.0.1.1
.0.0.0.0.0.1.1.1
.1.1.1.0.0.0.0.0
.1.1.0.1.0.0.0.0
.0.0.1.1.0.0.0.0
.0.0.1.1.0.0.0.0

Crossrefs

Sequence in context: A294367 A339495 A146694 * A147500 A300445 A115238

Adjacent sequences: A146047 A146048 A146049 * A146051 A146052 A146053

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved