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A195956 Number of n X 2 0..4 arrays with each element equal to the number its horizontal and vertical neighbors unequal to itself. 1

%I #9 May 08 2018 06:20:16

%S 1,1,6,5,5,14,21,29,54,93,149,254,437,733,1238,2109,3573,6046,10261,

%T 17405,29494,50013,84821,143806,243829,413469,701078,1188733,2015669,

%U 3417822,5795285,9826621,16662262,28252829,47906069,81230590,137736245

%N Number of n X 2 0..4 arrays with each element equal to the number its horizontal and vertical neighbors unequal to itself.

%C Column 2 of A195962.

%H R. H. Hardin, <a href="/A195956/b195956.txt">Table of n, a(n) for n = 1..200</a>

%F Empirical: a(n) = a(n-1) +3*a(n-3) -a(n-4) -2*a(n-6).

%F Empirical g.f.: x*(1 + 5*x^2 - 4*x^3 - 2*x^4 - 8*x^5) / ((1 - x)*(1 + x + x^2)*(1 - x - 2*x^3)). - _Colin Barker_, May 08 2018

%e All solutions for n=5:

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

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

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

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

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

%Y Cf. A195962.

%K nonn

%O 1,3

%A _R. H. Hardin_, Sep 25 2011

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)