A145955 Number of n X n binary arrays symmetric about main diagonal with all ones connected only in a zee 1,1 1,2 2,2 2,3 in any orientation.

1, 1, 1, 3, 9, 23, 125, 821, 6239, 71403, 1048093, 19913069, 517074745, 17642361171, 795865550951, 47901047706833, 3815017258032049, 403246928224172293, 56605968541991726917, 10536114891916229568297, 2602764408693859006627701

Offset

1,4

Links

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

Example

Maximal 8 X 8 example
.0.0.0.0.0.0.1.0
.0.0.0.0.0.0.1.1
.0.0.0.1.1.0.0.1
.0.0.1.0.1.1.0.0
.0.0.1.1.0.0.1.0
.0.0.0.1.0.0.1.1
.1.1.0.0.1.1.0.1
.0.1.1.0.0.1.1.0

Crossrefs

Sequence in context: A116659 A147508 A146472 * A129834 A029488 A198681

Adjacent sequences: A145952 A145953 A145954 * A145956 A145957 A145958

Keyword

nonn

Author

R. H. Hardin, Oct 25 2008

Status

approved