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A222439 Number of n X 3 0..3 arrays with entries increasing mod 4 by 0, 1 or 2 rightwards and downwards, starting with upper left zero.

%I A222439 #9 Mar 15 2018 08:12:28
%S A222439 9,147,2403,39285,642249,10499787,171655443,2806303725,45878770089,
%T A222439 750047661027,12262131106083,200467073061765,3277329775247529,
%U A222439 53579324981787867,875939945740498323,14320277248820697405
%N A222439 Number of n X 3 0..3 arrays with entries increasing mod 4 by 0, 1 or 2 rightwards and downwards, starting with upper left zero.
%C A222439 Column 3 of A222444.
%H A222439 R. H. Hardin, <a href="/A222439/b222439.txt">Table of n, a(n) for n = 1..210</a>
%F A222439 Empirical: a(n) = 18*a(n-1) - 27*a(n-2).
%F A222439 Empirical g.f.: 3*x*(3 - 5*x) / (1 - 18*x + 27*x^2). - _Colin Barker_, Mar 15 2018
%e A222439 Some solutions for n=3:
%e A222439 ..0..2..3....0..1..2....0..2..2....0..2..3....0..0..0....0..2..2....0..0..1
%e A222439 ..2..0..0....2..2..0....1..2..2....2..0..0....0..2..2....0..0..2....2..0..2
%e A222439 ..2..0..1....2..0..1....3..3..3....2..0..2....0..2..3....1..2..2....3..1..2
%Y A222439 Cf. A222444.
%K A222439 nonn
%O A222439 1,1
%A A222439 _R. H. Hardin_, Feb 20 2013