A188326 - OEIS

%I #5 Mar 31 2012 12:36:11

%S 0,2,4,20,86,424,2128,11200,60372,333254,1872728,10688284,61792756,

%T 361247006,2132290212,12692489494,76115308712,459476777038,

%U 2790092370660,17032567789840,104478722395496,643682329681246,3981493201581658

%N Number of nondecreasing arrangements of n nonzero numbers in -n..n with sum zero

%C Column 2 of A188333

%H R. H. Hardin, <a href="/A188326/b188326.txt">Table of n, a(n) for n = 1..31</a>

%e Some solutions for n=6

%e .-6...-4...-6...-4...-4...-5...-6...-4...-6...-4...-6...-6...-5...-6...-5...-3

%e .-5...-4...-3...-1...-3...-2...-5...-3...-6...-4...-3...-6...-4...-5...-4...-1

%e ..1...-2...-3...-1...-2...-2...-2...-2...-3...-1....2....2...-3....1...-2...-1

%e ..1....3....3...-1...-1....1....3...-2....3...-1....2....2....2....2....2...-1

%e ..4....3....4....2....4....2....4....5....6....5....2....3....5....3....3....1

%e ..5....4....5....5....6....6....6....6....6....5....3....5....5....5....6....5

%K nonn

%O 1,2

%A _R. H. Hardin_ Mar 28 2011