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A206989 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 1 1 1 vertically.

%I A206989 #11 Jun 17 2018 14:36:29
%S A206989 7,49,174,840,3858,17460,80070,365784,1670838,7636416,34893438,
%T A206989 159444240,728589330,3329288484,15213221238,69517022592,317658800982,
%U A206989 1451545657152,6632855083422,30308909178984,138496917825186,632863297956804
%N A206989 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 1 1 1 vertically.
%C A206989 Column 3 of A206994.
%H A206989 R. H. Hardin, <a href="/A206989/b206989.txt">Table of n, a(n) for n = 1..210</a>
%F A206989 Empirical: a(n) = 3*a(n-1) + 5*a(n-2) + 11*a(n-3) - 5*a(n-4) + a(n-5) - 3*a(n-6) + a(n-7) for n>9.
%F A206989 Empirical g.f.: x*(1 - x)*(7 + 35*x + 27*x^2 + 23*x^3 - 13*x^4 - 3*x^5 - x^6 + x^7) / (1 - 3*x - 5*x^2 - 11*x^3 + 5*x^4 - x^5 + 3*x^6 - x^7). - _Colin Barker_, Jun 17 2018
%e A206989 Some solutions for n=4:
%e A206989   1 0 1    0 0 1    0 1 1    1 1 1    0 0 1    1 0 0    1 1 0
%e A206989   1 0 0    0 1 1    0 0 1    0 0 1    1 1 1    0 0 1    1 0 1
%e A206989   0 1 1    0 1 0    1 0 0    0 1 0    1 0 0    0 1 0    0 1 1
%e A206989   0 0 1    0 0 1    0 1 1    1 0 1    0 0 1    0 0 1    1 1 0
%Y A206989 Cf. A206994.
%K A206989 nonn
%O A206989 1,1
%A A206989 _R. H. Hardin_, Feb 14 2012