A145938 Number of n X n binary arrays symmetric about main diagonal with all ones connected only in a 2X2 elbow 1,1 1,2 2,1 in any orientation.

1, 3, 7, 23, 131, 971, 9431, 139347, 2886057, 82544813, 3341873733, 191910369845, 15522222886741, 1764362997792863, 282874498672615023, 64026362228967252845, 20418507275512768653401, 9173719646436780783498511

Offset

1,2

Links

Table of n, a(n) for n=1..18.

Example

Maximal 8 X 8 example
.1.1.0.1.0.1.1.0
.1.0.1.1.0.1.0.1
.0.1.0.0.1.0.1.1
.1.1.0.0.1.1.0.0
.0.0.1.1.0.0.1.1
.1.1.0.1.0.0.1.0
.1.0.1.0.1.1.0.1
.0.1.1.0.1.0.1.1

Crossrefs

Sequence in context: A268140 A133788 A120271 * A329875 A048721 A113824

Adjacent sequences: A145935 A145936 A145937 * A145939 A145940 A145941

Keyword

nonn

Author

R. H. Hardin, Oct 25 2008

Status

approved