A145940 Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only in a 2 X 2 elbow 1,1 1,2 2,1 in any orientation.

1, 1, 1, 1, 3, 3, 7, 7, 23, 23, 131, 131, 971, 971, 9431, 9431, 139347, 139347, 2886057, 2886057, 82544813, 82544813, 3341873733, 3341873733, 191910369845, 191910369845, 15522222886741, 15522222886741, 1764362997792863

Offset

1,5

Links

Table of n, a(n) for n=1..29.

Example

Maximal 8 X 8 example:
  1 1 0 0 0 0 1 1
  1 0 1 0 0 1 0 1
  0 1 1 0 0 1 1 0
  0 0 0 0 0 0 0 0
  0 0 0 0 0 0 0 0
  0 1 1 0 0 1 1 0
  1 0 1 0 0 1 0 1
  1 1 0 0 0 0 1 1

Crossrefs

Sequence in context: A146599 A107222 A050613 * A147103 A003133 A021300

Adjacent sequences: A145937 A145938 A145939 * A145941 A145942 A145943

Keyword

nonn

Author

R. H. Hardin, Oct 25 2008

Status

approved