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A274750 Number of 3 X n 0..2 arrays with no element equal to any value at offset (-1,-2) (0,-1) or (-1,0) and new values introduced in order 0..2.

%I A274750 #8 Jan 31 2019 02:12:33
%S A274750 2,9,34,133,518,2017,7858,30605,119214,464345,1808682,7044997,
%T A274750 27441030,106885713,416331266,1621654589,6316517406,24603508041,
%U A274750 95833284570,373280851061,1453968675382,5663362861249,22059401583154,85923718843693
%N A274750 Number of 3 X n 0..2 arrays with no element equal to any value at offset (-1,-2) (0,-1) or (-1,0) and new values introduced in order 0..2.
%H A274750 R. H. Hardin, <a href="/A274750/b274750.txt">Table of n, a(n) for n = 1..210</a>
%F A274750 Empirical: a(n) = 2*a(n-1) + 7*a(n-2) + 2*a(n-3) - 2*a(n-4).
%F A274750 Empirical g.f.: x*(2 + 5*x + 2*x^2 - 2*x^3) / ((1 + x)*(1 - 3*x - 4*x^2 + 2*x^3)). - _Colin Barker_, Jan 30 2019
%e A274750 Some solutions for n=4:
%e A274750 ..0..1..0..2. .0..1..2..0. .0..1..0..1. .0..1..0..1. .0..1..0..1
%e A274750 ..2..0..1..0. .1..2..1..2. .1..2..1..0. .1..2..1..2. .2..0..1..2
%e A274750 ..1..2..0..2. .2..0..2..1. .0..1..2..1. .0..1..2..0. .0..2..0..1
%Y A274750 Row 3 of A274749.
%K A274750 nonn
%O A274750 1,1
%A A274750 _R. H. Hardin_, Jul 04 2016