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Number of (n+1) X 3 0..3 arrays with every 2 X 2 subblock having the same number of equal diagonal or antidiagonal elements, and new values 0..3 introduced in row major order.
1

%I #9 Jun 15 2018 12:45:11

%S 85,1369,25945,520097,10690969,222329489,4648291369,97418918945,

%T 2043949959289,42905465857457,900849319640905,18916269750894785,

%U 397226844350640025,8341623469422864209,175172765404628220265

%N Number of (n+1) X 3 0..3 arrays with every 2 X 2 subblock having the same number of equal diagonal or antidiagonal elements, and new values 0..3 introduced in row major order.

%C Column 2 of A206383.

%H R. H. Hardin, <a href="/A206377/b206377.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 36*a(n-1) - 377*a(n-2) + 1398*a(n-3) - 2064*a(n-4) + 1008*a(n-5).

%F Empirical g.f.: x*(85 - 1691*x + 8706*x^2 - 16640*x^3 + 10320*x^4) / ((1 - x)*(1 - 2*x)*(1 - 21*x)*(1 - 12*x + 24*x^2)). - _Colin Barker_, Jun 15 2018

%e Some solutions for n=4:

%e ..0..0..1....0..0..0....0..0..0....0..0..1....0..0..0....0..0..0....0..0..0

%e ..0..1..1....0..1..0....1..1..1....1..2..2....1..0..1....1..0..1....0..1..0

%e ..0..0..1....3..0..0....0..0..0....1..3..0....1..1..1....0..2..0....1..1..1

%e ..0..2..0....0..1..0....1..1..1....1..2..0....0..1..3....3..0..3....0..1..2

%e ..1..0..0....2..0..2....2..2..2....0..2..3....1..3..2....2..3..3....1..3..1

%Y Cf. A206383.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 07 2012