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%I #7 Feb 24 2018 09:25:46
%S 2,8,25,81,264,857,2785,9050,29407,95557,310508,1008981,3278637,
%T 10653778,34618955,112492681,365539724,1187804297,3859714705,
%U 12541963050,40754524407,132429927677,430324878028,1398320635661,4543777736197
%N Number of n X 2 0..1 arrays with no element equal to more than two horizontal or vertical neighbors, with new values 0..1 introduced in row major order.
%C Column 2 of A240484.
%H R. H. Hardin, <a href="/A240478/b240478.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) + a(n-2) - 2*a(n-4).
%F Empirical g.f.: x*(2 + 2*x - x^2 - 2*x^3) / (1 - 3*x - x^2 + 2*x^4). - _Colin Barker_, Feb 24 2018
%e Some solutions for n=4:
%e ..0..0....0..0....0..1....0..1....0..0....0..0....0..0....0..1....0..0....0..1
%e ..1..0....0..1....1..0....1..0....0..0....0..1....1..1....0..1....1..1....1..0
%e ..0..0....0..1....0..1....0..0....1..1....1..0....0..0....0..0....1..1....0..1
%e ..0..1....1..1....1..1....0..1....0..1....1..0....1..0....1..1....0..0....0..0
%Y Cf. A240484.
%K nonn
%O 1,1
%A _R. H. Hardin_, Apr 06 2014
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