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%I #8 Jan 09 2019 12:11:53
%S 2,12,20,54,120,284,660,1540,3592,8376,19536,45560,106256,247808,
%T 577936,1347856,3143456,7331136,17097600,39874848,92995712,216883648,
%U 505813824,1179653824,2751176576,6416265856,14963949568,34898770048,81390554368
%N Number of n X 3 integer arrays with each element equal to the number of horizontal and antidiagonal neighbors less than or equal to itself.
%H R. H. Hardin, <a href="/A266050/b266050.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - 2*a(n-3) - 2*a(n-4).
%F Empirical g.f.: 2*x*(1 + 4*x - 4*x^2 - 3*x^3) / (1 - 2*x - 2*x^2 + 2*x^3 + 2*x^4). - _Colin Barker_, Jan 09 2019
%e Some solutions for n=4:
%e ..0..3..1....1..0..2....1..0..2....1..1..2....1..0..1....1..0..1....1..1..2
%e ..1..0..2....2..1..2....2..0..2....2..0..2....1..4..1....1..4..0....2..0..2
%e ..2..0..2....0..1..2....2..0..2....2..0..1....1..0..2....0..4..1....2..0..2
%e ..2..0..1....2..1..1....2..1..0....1..3..0....2..1..0....1..0..1....2..0..1
%Y Column 3 of A266055.
%K nonn
%O 1,1
%A _R. H. Hardin_, Dec 20 2015
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