A145862 Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only in two by two blocks.

1, 2, 1, 2, 2, 5, 3, 12, 6, 32, 16, 104, 49, 441, 169, 2087, 742, 12047, 3848, 83725, 23784, 695140, 176890, 6907583, 1574720, 82485542, 16764539, 1176502867, 214487123, 20130478473

Offset

1,2

Links

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

Example

Maximal 7 X 7 example:
  0 0 0 0 0 0 0
  0 1 1 0 1 1 0
  0 1 1 0 1 1 0
  0 0 0 0 0 0 0
  0 1 1 0 1 1 0
  0 1 1 0 1 1 0
  0 0 0 0 0 0 0

Crossrefs

Sequence in context: A128978 A325110 A357888 * A364536 A058701 A004559

Adjacent sequences: A145859 A145860 A145861 * A145863 A145864 A145865

Keyword

nonn

Author

R. H. Hardin, Oct 22 2008

Status

approved