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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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 25 2008
STATUS
approved

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)