|
%I #6 Oct 27 2013 09:53:08
%S 0,3,15,21,135,177,1155,1509,9855,12873,84075,109821,717255,936897,
%T 6118995,7992789,52201935,68187513,445341435,581716461,3799265175,
%U 4962698097,32412020835,42337417029,276511126815,361185960873
%N Number of nX3 0..2 black 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 A230661
%H R. H. Hardin, <a href="/A230658/b230658.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*(-1-5*x+2*x^2) / ( 1-9*x^2+4*x^4 ). - _R. J. Mathar_, Oct 27 2013
%e Some solutions for n=5
%e ..x..0..x....x..2..x....x..1..x....x..0..x....x..2..x....x..2..x....x..2..x
%e ..1..x..2....0..x..0....0..x..1....2..x..0....0..x..0....2..x..0....0..x..0
%e ..x..1..x....x..0..x....x..2..x....x..2..x....x..2..x....x..0..x....x..1..x
%e ..2..x..2....2..x..0....1..x..0....0..x..2....0..x..0....0..x..0....0..x..1
%e ..x..0..x....x..2..x....x..1..x....x..0..x....x..2..x....x..2..x....x..2..x
%K nonn
%O 1,2
%A _R. H. Hardin_, Oct 27 2013
| 