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%I #9 Nov 29 2018 15:41:06
%S 226,3250,46684,670690,9635410,138426508,1988695378,28570462642,
%T 410455690300,5896784936386,84715776652690,1217063686620268,
%U 17484866170347826,251195190815325682,3608779345177708828
%N Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock summing to 3 4 5 6 7 8 or 9.
%H R. H. Hardin, <a href="/A251500/b251500.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 13*a(n-1) + 21*a(n-2) - 18*a(n-3) - 24*a(n-4).
%F Empirical g.f.: 2*x*(113 + 156*x - 156*x^2 - 192*x^3) / (1 - 13*x - 21*x^2 + 18*x^3 + 24*x^4). - _Colin Barker_, Nov 29 2018
%e Some solutions for n=3:
%e ..0..0....2..3....3..1....2..2....2..1....2..3....0..3....2..0....0..3....3..0
%e ..3..0....2..0....2..1....0..3....0..3....2..1....1..3....0..1....0..0....0..0
%e ..1..3....3..0....1..1....3..3....3..0....1..3....2..0....0..3....3..3....1..3
%e ..1..1....1..1....3..2....1..1....2..0....0..0....2..0....1..3....1..1....1..0
%Y Column 1 of A251507.
%K nonn
%O 1,1
%A _R. H. Hardin_, Dec 03 2014
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