login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Number of -2..2 arrays x(0..n-1) of n elements with zero sum and no two neighbors equal
1

%I #8 Dec 30 2012 04:01:50

%S 1,4,14,52,200,708,2642,10000,37984,144876,554120,2128672,8204180,

%T 31697564,122734614,476170124,1850664202,7204005752,28081918548,

%U 109604285492,428278469018,1675246478864,6559126501510,25703606447364

%N Number of -2..2 arrays x(0..n-1) of n elements with zero sum and no two neighbors equal

%C Column 2 of A199704

%H R. H. Hardin, <a href="/A199698/b199698.txt">Table of n, a(n) for n = 1..200</a>

%e Some solutions for n=5

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

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Nov 09 2011