%I
%S 0,6,10,36,94,274,768,2182,6170,17476,49470,140066,396544,1122694,
%T 3178538,8999012,25477790,72132146,204218880,578179846,1636929594,
%U 4634437764,13120914558,37147634242,105171535360,297759253766
%N Number of 0..3 arrays of length n with each element differing from at least one neighbor by 2 or more.
%C Column 3 of A221524.
%H R. H. Hardin, <a href="/A221519/b221519.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = a(n1) +4*a(n2) +3*a(n3) +a(n4).
%F Empirical g.f.: 2*x^2*(3 + 2*x + x^2) / ((1 + x)*(1  2*x  2*x^2  x^3)).  _Colin Barker_, Oct 18 2017
%e Some solutions for n=6
%e ..0....2....0....2....3....0....0....3....3....2....0....1....3....1....3....1
%e ..3....0....3....0....0....2....3....1....0....0....2....3....0....3....1....3
%e ..0....0....0....2....1....1....1....3....0....2....3....2....1....0....1....2
%e ..1....3....3....3....3....3....3....2....2....0....0....0....3....1....3....0
%e ..3....3....2....0....3....2....3....0....3....2....0....3....0....3....0....3
%e ..1....1....0....3....0....0....1....3....1....0....3....1....3....1....3....0
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 19 2013
