A146159 Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only either as two by three or three by two blocks.

1, 1, 1, 1, 7, 15, 60, 184, 747, 3499, 25726, 170389, 1816278, 17509129, 246038108, 3281197739, 66149680918, 1268005261759, 37496297507935, 1034674372954972, 43395951886928470

Offset

1,5

Links

Table of n, a(n) for n=1..21.

Example

Maximal 8 X 8 example
.1.1.0.1.1.0.0.0
.1.1.0.1.1.0.1.1
.1.1.0.1.1.0.1.1
.0.0.0.0.0.0.1.1
.1.1.0.0.0.0.0.0
.1.1.0.1.1.0.1.1
.1.1.0.1.1.0.1.1
.0.0.0.1.1.0.1.1

Crossrefs

Sequence in context: A145978 A037376 A141548 * A187986 A039789 A279882

Adjacent sequences: A146156 A146157 A146158 * A146160 A146161 A146162

Keyword

nonn

Author

R. H. Hardin, Oct 27 2008

Status

approved