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A230647 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).

%I A230647 #8 Jun 02 2025 08:43:38
%S A230647 0,3,3,21,27,177,231,1509,1971,12873,16815,109821,143451,936897,
%T A230647 1223799,7992789,10440387,68187513,89068287,581716461,759853035,
%U A230647 4962698097,6482404167,42337417029,55302225363,361185960873,471790411599
%N A230647 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 A230647 Column 3 of A230652
%H A230647 R. H. Hardin, <a href="/A230647/b230647.txt">Table of n, a(n) for n = 1..210</a>
%F A230647 Empirical: a(n) = 9*a(n-2) -4*a(n-4).
%F A230647 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 A230647 Some solutions for n=5
%e A230647 ..0..x..0....0..x..0....1..x..1....0..x..0....2..x..2....0..x..0....2..x..2
%e A230647 ..x..2..x....x..2..x....x..1..x....x..2..x....x..0..x....x..2..x....x..0..x
%e A230647 ..2..x..0....0..x..0....1..x..1....0..x..2....1..x..1....2..x..2....1..x..2
%e A230647 ..x..0..x....x..2..x....x..2..x....x..0..x....x..1..x....x..0..x....x..1..x
%e A230647 ..2..x..2....0..x..0....0..x..0....2..x..2....1..x..1....2..x..2....1..x..1
%K A230647 nonn
%O A230647 1,2
%A A230647 _R. H. Hardin_, Oct 27 2013