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%I #8 Jul 17 2018 15:44:51
%S 20,80,304,1144,4232,15536,56616,205400,742608,2678752,9648024,
%T 34716712,124861664,449008336,1614830152,5809328408,20907961552,
%U 75287770240,271263934328,977981837448,3528166785472,12736459731632,46007299834152
%N Number of -2..2 arrays x(i) of n+1 elements i=1..n+1 with x(i)+x(j), x(i+1)+x(j+1), -(x(i)+x(j+1)), and -(x(i+1)+x(j)) having three or four distinct values for every i<=n and j<=n.
%H R. H. Hardin, <a href="/A211463/b211463.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 5*a(n-1) + 9*a(n-2) - 57*a(n-3) - 36*a(n-4) + 196*a(n-5) + 96*a(n-6) - 124*a(n-7) + 24*a(n-8).
%F Empirical g.f.: 4*x*(5 - 5*x - 69*x^2 + 11*x^3 + 264*x^4 + 92*x^5 - 150*x^6 + 30*x^7) / ((1 - 2*x - 6*x^2)*(1 - x - 6*x^2 + 2*x^3)*(1 - 2*x - 5*x^2 + 2*x^3)). - _Colin Barker_, Jul 17 2018
%e Some solutions for n=5:
%e .-1...-2....1....2...-2....2...-1...-2....1....1...-2...-2...-1....2....1...-2
%e ..2....1...-1....0....1...-2....1....2...-2...-2....1....2....2....0....0....0
%e ..0....0...-2...-1....2....1...-1....1....0...-1....2....1....1...-1....1...-1
%e ..2....1....1....2....0...-2....1...-1....2...-2...-2...-1....0....0...-2....0
%e .-1...-2...-1....0....1....2....0....2...-2....0....1....0...-1....1....0....2
%e ..0....2....0....1....0....0....1...-2....0...-1....0....1....0....2....2...-1
%K nonn
%O 1,1
%A _R. H. Hardin_, Apr 12 2012
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