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 A201874 Number of zero-sum -n..n arrays of 3 elements with first and second differences also in -n..n. 2

%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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Last modified September 8 01:34 EDT 2024. Contains 375749 sequences. (Running on oeis4.)