A206866 - OEIS

%I #11 Jun 17 2018 14:36:44

%S 7,49,211,889,3967,17737,78799,350017,1555843,6915889,30739447,

%T 136629265,607288711,2699272273,11997693379,53327205481,237028156975,

%U 1053540057337,4682762813455,20813890672513,92513343672307,411202253906785

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

%C Column 3 of A206871.

%H R. H. Hardin, <a href="/A206866/b206866.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 4*a(n-1) + 8*a(n-3) + 4*a(n-4) - 2*a(n-5) - a(n-6).

%F Empirical g.f.: x*(7 + 21*x + 15*x^2 - 11*x^3 - 9*x^4 - x^5) / (1 - 4*x - 8*x^3 - 4*x^4 + 2*x^5 + x^6). - _Colin Barker_, Jun 17 2018

%e Some solutions for n=4:

%e   0 1 0    1 1 1    0 1 1    1 1 0    0 1 0    0 1 1    0 0 1

%e   1 0 1    1 1 0    1 1 0    0 0 1    1 0 0    0 1 1    0 0 1

%e   0 0 1    1 0 0    1 1 0    0 0 1    1 0 1    0 1 1    1 1 1

%e   0 1 0    1 0 1    1 0 1    1 0 0    1 1 0    0 1 1    0 0 1

%Y Cf. A206871.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 13 2012