A145957 Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only in a zee 1,1 1,2 2,2 2,3 in any orientation.

1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 9, 9, 23, 23, 125, 125, 821, 821, 6239, 6239, 71403, 71403, 1048093, 1048093, 19913069, 19913069, 517074745, 517074745, 17642361171, 17642361171

Offset

1,9

Links

Table of n, a(n) for n=1..30.

Example

Maximal 9 X 9 example:
  0 0 1 0 0 0 1 0 0
  0 0 1 1 0 1 1 0 0
  1 1 0 1 0 1 0 1 1
  0 1 1 0 0 0 1 1 0
  0 0 0 0 0 0 0 0 0
  0 1 1 0 0 0 1 1 0
  1 1 0 1 0 1 0 1 1
  0 0 1 1 0 1 1 0 0
  0 0 1 0 0 0 1 0 0

Crossrefs

Sequence in context: A146394 A147510 A146474 * A214439 A287479 A128019

Adjacent sequences: A145954 A145955 A145956 * A145958 A145959 A145960

Keyword

nonn

Author

R. H. Hardin, Oct 25 2008

Status

approved