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%I #10 Feb 15 2018 08:13:23
%S 3,5,15,21,27,47,57,67,97,111,125,165,183,201,251,273,295,355,381,407,
%T 477,507,537,617,651,685,775,813,851,951,993,1035,1145,1191,1237,1357,
%U 1407,1457,1587,1641,1695,1835,1893,1951,2101,2163,2225,2385,2451,2517
%N Number of zero-sum -n..n arrays of 3 elements with first and second differences also in -n..n.
%C Row 3 of A201873.
%H R. H. Hardin, <a href="/A201874/b201874.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = a(n-1) +2*a(n-3) -2*a(n-4) -a(n-6) +a(n-7).
%F Empirical g.f.: x*(3 + 2*x + x^2)*(1 + 3*x^2 - 2*x^3 + x^4) / ((1 - x)^3*(1 + x + x^2)^2). - _Colin Barker_, Feb 15 2018
%e Some solutions for n=12:
%e .-2....8...-2...-9....2..-10....9....1....0...-5...-3....5...-6...11....3....2
%e ..3...-4....0....1...-3....1....0....1...-3....4....0...-2....0...-1....4...-2
%e .-1...-4....2....8....1....9...-9...-2....3....1....3...-3....6..-10...-7....0
%K nonn
%O 1,1
%A _R. H. Hardin_, Dec 06 2011
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