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%I #9 Jul 14 2018 05:56:18
%S 0,9,90,657,4230,25533,148410,842265,4704750,25994709,142528770,
%T 777216177,4221470070,22863109293,123563792970,666766408905,
%U 3593844532350,19354295087109,104165322930450,560359838547297
%N Number of (n+1) X 2 0..2 arrays containing all values 0..2 with every 2 X 2 subblock having one or two distinct values, and new values 0..2 introduced in row major order.
%C Column 1 of A210095.
%H R. H. Hardin, <a href="/A210088/b210088.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 10*a(n-1) - 27*a(n-2) + 10*a(n-3) + 8*a(n-4).
%F Empirical g.f.: 9*x^2 / ((1 - x)*(1 - 4*x)*(1 - 5*x - 2*x^2)). - _Colin Barker_, Jul 14 2018
%e Some solutions for n=4:
%e ..0..0....0..0....0..1....0..0....0..1....0..0....0..0....0..1....0..0....0..1
%e ..1..0....0..0....0..0....1..1....1..1....0..1....0..1....1..1....0..1....0..1
%e ..1..0....0..0....1..0....1..0....0..0....0..0....0..0....1..0....0..0....0..0
%e ..0..0....1..1....0..0....1..1....1..1....0..2....2..0....1..1....0..2....2..0
%e ..0..2....1..2....0..2....1..2....1..2....2..0....0..0....2..1....0..2....2..2
%Y Cf. A210095.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 17 2012
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