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%I #12 Oct 26 2018 14:30:58
%S 1,3,6,16,40,84,208,474,1047,2530,5668,12907,30446,68427,157875,
%T 366480,830089,1920870,4421253,10083067,23303103,53453752,122448587,
%U 282350403,647215090,1486007814,3420002865,7842656682,18022838258,41428828907
%N Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or two plus the sum of elements above it or one plus the sum of the elements diagonally to its northwest, modulo 4.
%H R. H. Hardin, <a href="/A239980/b239980.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 2*a(n-2) + 10*a(n-3) - a(n-4) - 5*a(n-5) - 15*a(n-6) + a(n-7) + 4*a(n-8) + 2*a(n-9) + 10*a(n-10) + 5*a(n-11) - 6*a(n-13).
%F Empirical g.f.: x*(1 + 3*x + 4*x^2 - x^4 + 4*x^6 - 4*x^7 - 6*x^8 + 6*x^9 + 6*x^10 - 4*x^12) / (1 - 2*x^2 - 10*x^3 + x^4 + 5*x^5 + 15*x^6 - x^7 - 4*x^8 - 2*x^9 - 10*x^10 - 5*x^11 + 6*x^13). - _Colin Barker_, Oct 26 2018
%e Some solutions for n=4:
%e ..3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0
%e ..2..1....2..1....2..1....2..3....2..1....3..1....3..1....3..1....2..1....2..1
%e ..2..1....2..0....2..0....2..0....2..1....2..1....3..2....3..1....2..1....2..0
%e ..3..2....3..1....3..0....3..2....3..1....3..1....2..3....2..1....2..1....3..2
%Y Column 2 of A239986.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 30 2014
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