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Number of n X n symmetric 0..4 arrays with no element equal to any horizontal or vertical neighbor, containing at least one 4 and with new values 0..4 introduced in lower triangular row major order
1

%I #6 Dec 18 2015 18:17:42

%S 0,0,9,4369,3042328,5698808287,33317286304173,628998137157508637,

%T 38569165397999629055394,7686739047191692875345982285,

%U 4979433998253869605167632947630885

%N Number of n X n symmetric 0..4 arrays with no element equal to any horizontal or vertical neighbor, containing at least one 4 and with new values 0..4 introduced in lower triangular row major order

%H R. H. Hardin, <a href="/A193310/b193310.txt">Table of n, a(n) for n = 1..12</a>

%e Some solutions for 4X4

%e ..0..1..3..2....0..1..2..3....0..1..0..4....0..1..2..4....0..1..2..0

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

%e ..3..0..4..0....2..3..2..3....0..3..2..1....2..0..3..4....2..1..3..4

%e ..2..1..0..2....3..2..3..4....4..0..1..3....4..1..4..0....0..2..4..2

%K nonn

%O 1,3

%A _R. H. Hardin_ Jul 22 2011