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 A210923 Number of n X n 0..3 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order 1

%I

%S 1,5,166,35207,30211455,99371076165,1250065064815292,

%T 60143467055359131310,11066941546543240934864887,

%U 7788436930452056534815427874703,20963150916521213172749181596782816735

%N Number of n X n 0..3 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order

%H R. H. Hardin, <a href="/A210923/b210923.txt">Table of n, a(n) for n = 1..12</a>

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Mar 29 2012

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Last modified March 22 04:35 EDT 2023. Contains 361413 sequences. (Running on oeis4.)