A230835 - OEIS

%I #9 Sep 24 2018 02:47:24

%S 0,2,22,162,1202,8974,66990,500018,3732178,27857358,207930158,

%T 1552011826,11584373970,86466944462,645398059822,4817316700722,

%U 35956941366482,268386264128974,2003262347565870,14952553724011058,111607380401824978

%N Number of n X 2 0..3 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 4, and upper left element zero.

%H R. H. Hardin, <a href="/A230835/b230835.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 8*a(n-1) - 5*a(n-2) + 8*a(n-3) - 4*a(n-4).

%F Empirical g.f.: 2*x^2*(1 + 3*x - 2*x^2) / ((1 + x^2)*(1 - 8*x + 4*x^2)). - _Colin Barker_, Sep 22 2018

%e Some solutions for n=3:

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

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

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

%Y Column 2 of A230840.

%K nonn

%O 1,2

%A _R. H. Hardin_, Oct 31 2013