A202041 - OEIS

%I #5 Mar 31 2012 12:36:46

%S 3,19,73,335,1593,7669,37311,184335,919889,4620477,23332387,118371541,

%T 602858159,3080279011,15782030681,81053501795,417143999201,

%U 2150782607289,11107401645291,57445755808701,297487456185331,1542374070100235

%N Number of zero-sum nX2 -1..1 arrays with every element unequal to at most two horizontal and vertical neighbors

%C Column 2 of A202047

%H R. H. Hardin, <a href="/A202041/b202041.txt">Table of n, a(n) for n = 1..93</a>

%e Some solutions for n=7

%e ..0..1....0..1...-1.-1....1..0...-1..0...-1..0....1.-1....1..1...-1..1....1..1

%e .-1.-1....1..1...-1.-1....0..0....1..0....1..1...-1..1...-1..1...-1..0....0.-1

%e ..1..1....0..0....1.-1...-1.-1....1..0...-1.-1...-1..1...-1..1...-1..0....0.-1

%e ..0..0....0..0....1..0....1..1....1..0....1.-1...-1..0....1..1....0..0....1..1

%e ..1.-1....0.-1....1..0....0..1...-1.-1....1.-1....0..0...-1.-1....0..1....1.-1

%e ..1.-1...-1.-1....1..1....0..0...-1.-1....1.-1....0..0...-1.-1....0..1...-1.-1

%e .-1..0....0..0....0..0...-1.-1....1..1....0..1....0..1....0..0...-1..1....0..0

%K nonn

%O 1,1

%A _R. H. Hardin_ Dec 10 2011