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Number of n X n symmetric 0..3 arrays with no element equal to the sum or difference mod 4 of any two of its horizontal and vertical neighbors
1

%I #7 Dec 18 2015 18:17:43

%S 4,17,77,1099,33151,2100065,268468949,68719995395,35184382602599,

%T 36028797316842905,73786976306927999773,302231454904310883795947,

%U 2475880078570809183639151007,40564819207303345898201553712849

%N Number of n X n symmetric 0..3 arrays with no element equal to the sum or difference mod 4 of any two of its horizontal and vertical neighbors

%H R. H. Hardin, <a href="/A193782/b193782.txt">Table of n, a(n) for n = 1..31</a>

%e Some solutions for 4X4

%e ..3..3..3..3....3..3..1..3....3..3..1..1....1..3..3..1....1..1..3..1

%e ..3..1..1..3....3..3..1..1....3..3..3..3....3..3..1..1....1..1..3..3

%e ..3..1..1..3....1..1..1..3....1..3..1..1....3..1..3..1....3..3..3..3

%e ..3..3..3..1....3..1..3..3....1..3..1..1....1..1..1..3....1..3..3..3

%K nonn

%O 1,1

%A _R. H. Hardin_ Aug 05 2011