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Number of arrays of n integers in -4..4 with sum zero and equal numbers of elements greater than zero and less than zero
1

%I #5 Mar 31 2012 12:36:45

%S 1,9,25,313,1401,15681,90609,909945,6105913,57290209,421304049,

%T 3799765201,29595440785,261111392985,2109792275145,18400232046585,

%U 152275971653625,1320864136716225,11107129707193809,96160509723165393

%N Number of arrays of n integers in -4..4 with sum zero and equal numbers of elements greater than zero and less than zero

%C Column 4 of A201811

%H R. H. Hardin, <a href="/A201807/b201807.txt">Table of n, a(n) for n = 1..210</a>

%e Some solutions for n=7

%e .-3....0...-1....4...-2...-4....4...-2....4....4...-3....2....4...-4....1....2

%e ..0....2....2...-4...-2...-4...-4...-1....0....0....0...-4....0...-4...-3...-3

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

%e ..2...-2....0....0....2....0....0....2...-2....1....4...-3...-4....0...-1....0

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

%e ..4....1...-1....3....1...-3....4....0....1...-2....3...-2...-2....4...-2....4

%e ..3...-1...-4....3....0....4....1....1...-3....4....2....0...-4....4....0....3

%K nonn

%O 1,2

%A _R. H. Hardin_ Dec 05 2011