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%I #8 Sep 25 2018 14:50:41
%S 0,32,128,2080,18688,209440,2150784,22847008,239510016,2523778080,
%T 26540458624,279321664544,2938791541504,30923196075552,
%U 325371816285056,3423602175951392,36023310011880448,379040068394055712
%N Number of n X 4 0..3 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero.
%H R. H. Hardin, <a href="/A231045/b231045.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 8*a(n-1) + 33*a(n-2) - 68*a(n-3).
%F Empirical g.f.: 32*x^2*(1 - 4*x) / (1 - 8*x - 33*x^2 + 68*x^3). - _Colin Barker_, Sep 25 2018
%e Some solutions for n=4:
%e ..0..1..2..3....0..3..2..3....0..3..0..1....0..3..2..3....0..3..2..1
%e ..0..3..0..3....2..1..0..3....2..1..2..3....0..1..0..3....0..1..0..1
%e ..2..3..2..1....0..1..2..3....2..3..0..1....0..1..2..1....2..3..0..3
%e ..0..1..0..3....2..3..0..3....0..1..2..1....2..3..0..3....0..1..2..1
%Y Column 4 of A231049.
%K nonn
%O 1,2
%A _R. H. Hardin_, Nov 03 2013
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