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%I #5 Mar 31 2012 12:36:12
%S 17,153,497,4201,22229,181449,1264985,10396729,81850801,684867741,
%T 5680170701,48268778269,410276328441,3525682027185,30364372592101,
%U 262996695840081,2283098828435689,19886474577091625,173553193860930897
%N Number of arrangements of n+1 numbers x(i) in -4..4 with the sum of x(i)*x(i+1) equal to zero
%C Column 4 of A188358
%H R. H. Hardin, <a href="/A188353/b188353.txt">Table of n, a(n) for n = 1..60</a>
%e Some solutions for n=5
%e ..0...-1...-1....0....0....0....0....0....1...-1....3....3...-1....2...-4....1
%e ..2...-4...-3....0...-1....0...-4....4...-2...-1....2...-1....2....2...-1...-3
%e ..1....4...-3....4...-3....4...-2...-1....0....1...-1...-3...-2...-4....4....3
%e ..1....3....4....0....4...-1....4....0...-2....2....0....0...-3...-4....0....3
%e .-3...-3...-4....0....3...-2....0....1....1....1...-1....4....3....2....1....3
%e ..0...-3...-4....4...-1...-1....3....4....4...-4....4....0....3...-2....0...-2
%K nonn
%O 1,1
%A _R. H. Hardin_ Mar 28 2011
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