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%I #4 Mar 31 2012 12:36:11
%S 40,1284,12692,58824,193232,521124,1142180,2347608,4323448,7567844,
%T 12129300,19691552,29057776,42900188,61593740,86648240
%N Number of arrangements of 7 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero
%C Row 5 of A188249
%e Some solutions for n=4
%e ..1....2...-3...-1...-1....1...-1....4...-1....4...-1....4...-1....2....4....3
%e .-2....1....3....3...-2....1....3...-1....1....3....2....4...-3....3...-3...-2
%e ..4....4....4....3...-2....2....1...-4...-3...-3...-1....2...-3...-1...-4....1
%e ..2...-4...-4...-4...-2....3....2....3...-1....1....1...-2....4...-1...-1....4
%e .-3...-4...-4...-1....1...-2...-3....3....2....1....4....4....4...-2....4....2
%e .-4....3....3....2...-4....1...-4....3....1....1....1...-2...-2...-3...-3....4
%e ..1....2....3....2....1...-1....2...-2....1...-2...-3....2....4....4...-4...-3
%K nonn
%O 1,1
%A _R. H. Hardin_ Mar 25 2011
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