A146139 Number of n X n binary arrays symmetric about main diagonal with all ones connected only in a 5-point barb 1,1 1,2 2,2 2,3 3,2 in any orientation.

1, 1, 1, 1, 7, 21, 61, 403, 3415, 36395, 473261, 8291363, 204964495, 6738662861, 291876652529, 16526293766701, 1250870357604441, 127503882340930419, 17331789387120484429, 3122597067315836972733, 746394914944854757141353

Offset

1,5

Links

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

Example

Maximal 8 X 8 example
.0.0.1.1.0.1.1.0
.0.0.0.1.1.0.1.1
.1.0.0.1.0.0.1.0
.1.1.1.0.0.0.0.1
.0.1.0.0.0.1.1.1
.1.0.0.0.1.0.1.0
.1.1.1.0.1.1.0.0
.0.1.0.1.1.0.0.0

Crossrefs

Sequence in context: A001354 A200930 A088656 * A083596 A082541 A005032

Adjacent sequences: A146136 A146137 A146138 * A146140 A146141 A146142

Keyword

nonn

Author

R. H. Hardin, Oct 27 2008

Status

approved