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A208421 Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 0 1 1 vertically.

%I A208421 #8 Jul 02 2018 14:14:37
%S A208421 9,81,261,1269,5139,22509,95265,409239,1746639,7475751,31957515,
%T A208421 136685781,584484003,2499573411,10689072525,45711185121,195479542125,
%U A208421 835952734845,3574879817931,15287675934645,65376453864249
%N A208421 Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 0 1 1 vertically.
%C A208421 Row 4 of A208420.
%H A208421 R. H. Hardin, <a href="/A208421/b208421.txt">Table of n, a(n) for n = 1..210</a>
%F A208421 Empirical: a(n) = 3*a(n-1) + 7*a(n-2) - 6*a(n-3) - 3*a(n-4) + 2*a(n-5).
%F A208421 Empirical g.f.: 9*x*(1 + 6*x - 5*x^2 - 3*x^3 + 2*x^4) / (1 - 3*x - 7*x^2 + 6*x^3 + 3*x^4 - 2*x^5). - _Colin Barker_, Jul 02 2018
%e A208421 Some solutions for n=4:
%e A208421 ..0..1..0..1....0..1..1..1....0..1..1..0....1..0..1..0....1..0..1..0
%e A208421 ..0..1..0..1....1..0..1..0....0..1..1..0....1..1..0..0....1..0..1..1
%e A208421 ..1..0..1..0....0..1..0..0....1..0..1..1....1..0..1..1....1..1..1..0
%e A208421 ..0..1..0..1....1..0..1..1....0..1..0..0....1..1..0..0....1..0..1..1
%Y A208421 Cf. A208420.
%K A208421 nonn
%O A208421 1,1
%A A208421 _R. H. Hardin_, Feb 26 2012