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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. 0
1, 1, 1, 1, 1, 3, 17, 33, 77, 271, 971, 3963, 20443, 99229, 615963, 4003277, 33415251, 283218519, 3003051651, 32410844251, 438884364075 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 1 11:30 EST 2021. Contains 349429 sequences. (Running on oeis4.)