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 A211087 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors 1

%I

%S 1,9,324,35343,12487068,14118092100,51199696832895,595365272306224965,

%T 22199455509688700548632,2654252181204304007637930258,

%U 1017614219466672806577892453493568

%N 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors

%H R. H. Hardin, <a href="/A211087/b211087.txt">Table of n, a(n) for n = 1..12</a>

%e Some solutions for n=4

%e ..1..3..0..1....3..0..2..3....3..0..2..0....1..3..1..3....0..3..3..0

%e ..3..1..2..1....0..2..0..0....0..1..0..3....3..3..3..2....3..1..2..1

%e ..0..2..2..2....2..0..2..1....2..0..2..3....1..3..1..0....3..2..3..1

%e ..1..1..2..0....3..0..1..3....0..3..3..2....3..2..0..1....0..1..1..0

%K nonn

%O 1,2

%A _R. H. Hardin_ Mar 31 2012

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Last modified October 22 19:03 EDT 2020. Contains 337953 sequences. (Running on oeis4.)