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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. 0
1, 3, 7, 23, 131, 971, 9431, 139347, 2886057, 82544813, 3341873733, 191910369845, 15522222886741, 1764362997792863, 282874498672615023, 64026362228967252845, 20418507275512768653401, 9173719646436780783498511 (list; graph; refs; listen; history; text; internal format)
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 * A048721 A113824 A121883

Adjacent sequences:  A145935 A145936 A145937 * A145939 A145940 A145941

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 25 2008

STATUS

approved

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Last modified August 24 03:20 EDT 2019. Contains 326260 sequences. (Running on oeis4.)