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%I #7 Oct 01 2018 21:09:43
%S 18,142,1034,7756,58350,438540,3295580,24766738,186126146,1398767358,
%T 10511956032,78999000742,593689902080,4461672883324,33530172645330,
%U 251984515016934,1893703217109050,14231477177253100,106951786751372582
%N Number of (n+1) X (2+1) 0..1 arrays with every element equal to some horizontal, vertical, diagonal or antidiagonal neighbor, with top left element zero.
%H R. H. Hardin, <a href="/A231951/b231951.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 7*a(n-1) + 2*a(n-2) + 13*a(n-3) + 8*a(n-4).
%F Empirical g.f.: 2*x*(9 + 8*x + 2*x^2) / (1 - 7*x - 2*x^2 - 13*x^3 - 8*x^4). - _Colin Barker_, Oct 01 2018
%e Some solutions for n=5:
%e ..0..1..1....0..1..0....0..1..1....0..0..1....0..0..0....0..0..0....0..0..1
%e ..0..1..0....0..0..1....1..0..1....0..1..0....1..0..0....1..0..1....1..1..0
%e ..0..1..0....1..0..0....1..1..0....0..1..1....1..1..0....1..1..1....0..0..0
%e ..0..0..1....1..1..1....1..0..1....0..1..0....1..0..1....1..0..1....0..0..1
%e ..1..0..1....1..0..0....1..0..0....1..0..0....0..1..0....1..0..0....1..0..1
%e ..1..1..0....1..1..0....0..0..0....0..1..0....1..0..1....1..1..0....1..0..0
%Y Column 2 of A231957.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 15 2013