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A146049 Number of n X n binary arrays symmetric about main diagonal with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation. 0
1, 1, 1, 3, 13, 35, 181, 1303, 13131, 161693, 2592581, 57377381, 1720164275, 69927099465, 3715147371129, 261988046119405, 24980387570081613, 3210146525819915095, 550205755804555982181, 125514016677735094761717 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

Maximal 8 X 8 example

.0.0.0.0.0.0.1.1

.0.0.0.0.0.0.1.1

.0.0.0.1.1.1.0.1

.0.0.1.0.1.1.0.0

.0.0.1.1.0.0.1.1

.0.0.1.1.0.0.1.1

.1.1.0.0.1.1.0.1

.1.1.1.0.1.1.1.0

CROSSREFS

Sequence in context: A146741 A146725 A146424 * A061483 A128288 A113115

Adjacent sequences:  A146046 A146047 A146048 * A146050 A146051 A146052

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 26 2008

STATUS

approved

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Last modified November 18 14:37 EST 2019. Contains 329262 sequences. (Running on oeis4.)