A146021 Number of n X n binary arrays symmetric under 90 degree rotation with all ones connected only in a 2X4 el 1,1 1,2 1,3 1,4 2,4 with any orientation.

1, 1, 1, 1, 1, 3, 17, 33, 77, 271, 971, 3963, 20443, 99229, 615963, 4003277, 33415251, 283218519, 3003051651, 32410844251, 438884364075

Offset

1,6

Links

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

Example

Maximal 8 X 8 example
.1.0.0.0.1.1.1.1
.1.0.0.0.1.0.0.0
.1.0.0.0.0.0.0.0
.1.1.0.0.0.0.0.0
.0.0.0.0.0.0.1.1
.0.0.0.0.0.0.0.1
.0.0.0.1.0.0.0.1
.1.1.1.1.0.0.0.1

Crossrefs

Sequence in context: A214093 A309744 A115355 * A146133 A297735 A266062

Adjacent sequences: A146018 A146019 A146020 * A146022 A146023 A146024

Keyword

nonn

Author

R. H. Hardin, Oct 26 2008

Status

approved