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%I #8 Dec 29 2023 23:06:33
%S 7,231,1587,17903,194633,2232183,25952953,305979795,3640250461,
%T 43624267941,525774918227,6366440653727,77388201173481,
%U 943784967491137,11542145313593503,141498452574240619,1738344524754583621
%N Number of zero-sum n X 2 -3..3 arrays with every element unequal to at most two horizontal and vertical neighbors.
%C Column 2 of A201958.
%H R. H. Hardin, <a href="/A201955/b201955.txt">Table of n, a(n) for n = 1..68</a>
%e Some solutions for n=4
%e ..2..3...-3.-3...-2.-3...-2..3...-2..1....2.-3....2.-3....2..0...-3.-1....1.-2
%e ..0..0....2..2....1..1....0..0...-2..0....1..1....3.-3....0.-1....3..0....0..0
%e .-2.-2...-1.-1....2..2....1..1....2..0....0..0....3..0....0.-1....3..0....0..0
%e .-2..1....3..1....0.-1...-1.-2....2.-1...-1..0...-2..0....3.-3...-2..0....3.-2
%Y Cf. A201958.
%K nonn
%O 1,1
%A _R. H. Hardin_, Dec 06 2011
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