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%I #5 Mar 31 2012 12:35:55
%S 1,1,9,33,321,1411,10613,70449,534153,3908739,31172293,247959153,
%T 2040991681,16818777105,139873091535,1164007471357,9753589044027,
%U 82147216112609,696523301660651,5930891437147689,50682977439086169
%N Number of strings of n numbers x(i) in -4..4 with sums of x(i) and of x(i)*x(i+1) both zero
%C Column 4 of A183944
%H R. H. Hardin, <a href="/A183939/b183939.txt">Table of n, a(n) for n = 1..28</a>
%e Some solutions for n=6
%e ..0....3...-2....4....0...-1....1...-4....4....4...-2....0...-1....4....2....3
%e .-3...-2....0....0...-3....0....2....1....0....1...-1....4....2...-1...-1....2
%e ..0...-2....3....0...-3....0...-1...-4....1....2....2....0....1....2....2...-1
%e ..2...-2....2...-3....3...-2....0....1...-4...-3....1....0....0....0....1...-1
%e ..3...-1...-3...-4....0....0...-2....4...-1....0...-1....0....0...-3...-1....1
%e .-2....4....0....3....3....3....0....2....0...-4....1...-4...-2...-2...-3...-4
%K nonn
%O 1,3
%A _R. H. Hardin_ Jan 08 2011
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