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%I #5 Mar 31 2012 12:36:46
%S 19,335,2921,31753,359017,4188917,49553277,594443301,7206865523,
%T 88120417529,1084547246367,13417760493253,166705101517923,
%U 2078489858665207,25992085202674059,325869090446388117
%N Number of zero-sum nX4 -1..1 arrays with every element unequal to at most two horizontal and vertical neighbors
%C Column 4 of A202047
%H R. H. Hardin, <a href="/A202043/b202043.txt">Table of n, a(n) for n = 1..31</a>
%e Some solutions for n=4
%e ..1..1.-1.-1....1..1.-1..0...-1..1..1.-1....1.-1..1..1....0..1..1..0
%e .-1..1..1.-1....0.-1.-1..0....1..0..0.-1....1.-1..0..0....0..0..0..0
%e .-1..1..1.-1....0.-1..1..1....1..0..0.-1....1.-1..0..0....1.-1.-1.-1
%e .-1.-1..1..1...-1.-1..1..1....1..1.-1.-1...-1.-1..0..0....1.-1..0..0
%K nonn
%O 1,1
%A _R. H. Hardin_ Dec 10 2011
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