A230648 - OEIS

%I #6 Oct 27 2013 09:57:00

%S 0,9,21,123,531,2547,11745,54957,255753,1192623,5557191,25901847,

%T 120714693,562609041,2622085629,12220512675,56954899323,265444104699,

%U 1237128910377,5765764156725,26871924749169,125239314486231

%N Number of nX4 0..2 white square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j)

%C Column 4 of A230652

%H R. H. Hardin, <a href="/A230648/b230648.txt">Table of n, a(n) for n = 1..210</a>

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

%F Empirical: G.f. 3*x^2*(1+x)*(x^2-5*x+3) / ( 1-3*x-8*x^2+x^3+x^4 ). - _R. J. Mathar_, Oct 27 2013

%e Some solutions for n=5

%e ..0..x..0..x....0..x..0..x....2..x..0..x....1..x..1..x....0..x..0..x

%e ..x..2..x..0....x..2..x..1....x..0..x..2....x..1..x..1....x..2..x..2

%e ..0..x..2..x....0..x..1..x....2..x..2..x....2..x..1..x....2..x..1..x

%e ..x..2..x..0....x..2..x..0....x..0..x..0....x..0..x..2....x..0..x..1

%e ..0..x..0..x....0..x..2..x....2..x..2..x....2..x..0..x....2..x..2..x

%K nonn

%O 1,2

%A _R. H. Hardin_, Oct 27 2013