A146156 Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only either as two by three or three by two blocks.

1, 1, 1, 1, 1, 1, 2, 4, 7, 11, 20, 47, 126, 349, 1026, 3169, 10962, 42335, 178967, 817710, 4108982, 22332287, 134485764, 875416554, 6255533128, 48551931040, 415466055841, 3858971189964, 39521400790374, 437870905678969

Offset

1,7

Links

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

Example

Maximal 8 X 8 example
.0.0.0.1.1.0.0.0
.0.0.0.1.1.0.0.0
.0.0.0.1.1.0.0.0
.1.1.1.0.0.1.1.1
.1.1.1.0.0.1.1.1
.0.0.0.1.1.0.0.0
.0.0.0.1.1.0.0.0
.0.0.0.1.1.0.0.0

Crossrefs

Sequence in context: A018173 A288380 A369581 * A304916 A024927 A018077

Adjacent sequences: A146153 A146154 A146155 * A146157 A146158 A146159

Keyword

nonn

Author

R. H. Hardin, Oct 27 2008

Status

approved