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Number of -3..3 arrays x(0..n-1) of n elements with zero sum and no element more than one greater than the previous.
1

%I #8 Dec 02 2014 09:00:26

%S 1,4,13,42,132,428,1393,4561,15032,49889,166542,558744,1883028,

%T 6370957,21628455,73641852,251385571,860067894,2948380732,10124956970,

%U 34823894885,119940097035,413612099138,1427945022753,4934850614704

%N Number of -3..3 arrays x(0..n-1) of n elements with zero sum and no element more than one greater than the previous.

%C Column 3 of A199847.

%H R. H. Hardin, <a href="/A199842/b199842.txt">Table of n, a(n) for n = 1..200</a>

%e Some solutions for n=6

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

%e ..1....0....2....1....0....0....0....0....1....1....2....1....1....0....0....3

%e ..1....1....2...-1...-2....0....1....1....0...-1....2....2....2....1....1....1

%e .-1....1...-2....0...-1....0....0...-1....0...-1...-1...-1...-1....2....2...-1

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_, Nov 11 2011