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A206931 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 0 1 1 vertically.

%I A206931 #11 Jun 17 2018 14:37:03
%S A206931 7,49,211,811,2791,9055,28081,84403,247705,713857,2027929,5695201,
%T A206931 15845455,43747201,120004363,327401947,889103743,2404885423,
%U A206931 6482464537,17421401395,46696588561,124877198881,333267920209,887801858209
%N A206931 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 0 1 1 vertically.
%C A206931 Column 3 of A206936.
%H A206931 R. H. Hardin, <a href="/A206931/b206931.txt">Table of n, a(n) for n = 1..210</a>
%F A206931 Empirical: a(n) = 6*a(n-1) - 9*a(n-2) - 6*a(n-3) + 18*a(n-4) - 9*a(n-6) + a(n-8).
%F A206931 Empirical g.f.: x*(7 + 7*x - 20*x^2 + 28*x^3 - 8*x^4 - 8*x^5 + x^6 + x^7) / ((1 - x)*(1 + x)*(1 - 3*x + x^2)*(1 - x - x^2)*(1 - 2*x - x^2)). - _Colin Barker_, Jun 17 2018
%e A206931 Some solutions for n=4:
%e A206931   0 0 1    0 1 0    0 0 1    1 1 1    0 0 1    1 1 0    1 1 0
%e A206931   0 1 1    1 0 1    0 0 1    1 1 1    0 1 1    1 0 1    0 0 1
%e A206931   1 0 0    0 1 0    1 0 1    1 1 1    0 0 1    1 0 0    1 1 0
%e A206931   0 0 1    1 0 0    0 0 1    1 1 1    0 1 0    0 1 1    0 0 1
%Y A206931 Cf. A206936.
%K A206931 nonn
%O A206931 1,1
%A A206931 _R. H. Hardin_, Feb 13 2012