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A235881 Number of (n+1) X (5+1) 0..2 arrays with the minimum plus the upper median equal to the lower median plus the maximum in every 2 X 2 subblock. 1

%I

%S 921,1311,2109,3759,7221,14631,30909,67839,154821,368151,912909,

%T 2356719,6307221,17396871,49142109,141330399,411800421,1211020791,

%U 3584302509,10655388879,31771130421,94923319911,283989818109,850409172159

%N Number of (n+1) X (5+1) 0..2 arrays with the minimum plus the upper median equal to the lower median plus the maximum in every 2 X 2 subblock.

%H R. H. Hardin, <a href="/A235881/b235881.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 6*a(n-1) -11*a(n-2) +6*a(n-3).

%F Conjectures from _Colin Barker_, Oct 19 2018: (Start)

%F G.f.: 3*x*(307 - 1405*x + 1458*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).

%F a(n) = 3*(180 + 31*2^(1+n) + 3^n).

%F (End)

%e Some solutions for n=5:

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

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

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

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

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

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

%Y Column 5 of A235884.

%K nonn

%O 1,1

%A _R. H. Hardin_, Jan 16 2014

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Last modified October 18 12:19 EDT 2021. Contains 348067 sequences. (Running on oeis4.)