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%I #5 Mar 31 2012 12:36:11
%S 0,20,52,144,208,436,532,816,1072,1508,1668,2400,2592,3220,3940,4768,
%T 5024,6212,6500,7856,8944,9988,10340,12384,13280,14516,15796,17824,
%U 18272,21156,21636,23712,25472,27124,29124,32800,33376,35220,37300,41136,41776
%N Number of arrangements of 4 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero
%C Row 2 of A188249
%H R. H. Hardin, <a href="/A188250/b188250.txt">Table of n, a(n) for n = 1..135</a>
%e Some solutions for n=4
%e .-2...-3...-1....1....3....1....2...-2....1....3....3....3...-2....2...-4...-3
%e .-4...-1...-3...-4....2...-1....1...-3...-2...-2....1...-1....2...-3...-3...-1
%e ..1...-3...-3...-4....3....1....2....1....1...-1....1....3....1...-1....3....1
%e .-4....2....4....3...-4....2...-2...-3....4...-4...-4....2....2...-3...-1...-2
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 25 2011
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