A145860 Number of n X n binary arrays symmetric about main diagonal with all ones connected only in two by two blocks.

1, 2, 3, 6, 16, 49, 169, 742, 3848, 23784, 176890, 1574720, 16764539, 214487123, 3284115855, 60203667877, 1323062783686, 34845447884285, 1099257570874298, 41549582286031187, 1881714538522030500, 102107501292816609976

Offset

1,2

Links

Table of n, a(n) for n=1..22.

Example

Maximal 7 X 7 example
.1.1.0.0.0.1.1
.1.1.0.0.0.1.1
.0.0.1.1.0.0.0
.0.0.1.1.0.1.1
.0.0.0.0.0.1.1
.1.1.0.1.1.0.0
.1.1.0.1.1.0.0

Crossrefs

Sequence in context: A006402 A284417 A219024 * A305190 A087983 A340911

Adjacent sequences: A145857 A145858 A145859 * A145861 A145862 A145863

Keyword

nonn

Author

R. H. Hardin, Oct 22 2008

Status

approved