A230647 - OEIS

%I #6 Oct 27 2013 09:55:40

%S 0,3,3,21,27,177,231,1509,1971,12873,16815,109821,143451,936897,

%T 1223799,7992789,10440387,68187513,89068287,581716461,759853035,

%U 4962698097,6482404167,42337417029,55302225363,361185960873,471790411599

%N Number of nX3 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 3 of A230652

%H R. H. Hardin, <a href="/A230647/b230647.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 9*a(n-2) -4*a(n-4).

%F Empirical: G.f. -3*x^2*(2*x+1)*(x-1) / ( 1-9*x^2+4*x^4 ). - _R. J. Mathar_, Oct 27 2013

%e Some solutions for n=5

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

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_, Oct 27 2013