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URL: https://oeis.org/A180752

⇱ A180752 - OEIS

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A180752
Half the number of nX3 binary arrays with each element equal to at least two neighbors.
1
0, 1, 1, 2, 3, 7, 14, 31, 67, 148, 325, 717, 1580, 3485, 7685, 16950, 37383, 82451, 181850, 401083, 884615, 1951080, 4303241, 9491097, 20933272, 46169785, 101830665, 224594602, 495358987, 1092548639, 2409691878, 5314742743
OFFSET
1,4
COMMENTS
Column 3 of A180760
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-2) - a(n-3) - a(n-5).
Empirical: G.f.: -x^2*(-1+x+x^3+x^2) / ( (x-1)*(1+x)*(x^3+2*x-1) ). a(n)-a(n-2) = A052980(n-3). - R. J. Mathar, Mar 24 2018
CROSSREFS
Sequence in context: A205484 A385906 A151530 * A000642 A348530 A229734
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 20 2010
STATUS
approved