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A208874 Number of 3Xn 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

%I A208874 #7 Jul 22 2025 21:33:02
%S A208874 5,143,6520,307165,14493405,683903931,32271626438,1522813452263,
%T A208874 71857577327143,3390770839381669,160001593732718856,
%U A208874 7550056082308516761,356267369073405009281,16811323900505484274607,793282337427660173475274
%N A208874 Number of 3Xn 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.
%C A208874 Row 3 of A208872
%H A208874 R. H. Hardin, <a href="/A208874/b208874.txt">Table of n, a(n) for n = 1..210</a>
%F A208874 Empirical: a(n) = 61*a(n-1) -722*a(n-2) +3476*a(n-3) -7851*a(n-4) +8583*a(n-5) -4266*a(n-6) +720*a(n-7) for n>8
%e A208874 Some solutions for n=4
%e A208874 ..0..1..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
%e A208874 ..2..2..1..2....1..1..1..2....1..2..2..1....1..1..1..0....1..1..1..0
%e A208874 ..1..2..3..2....2..0..1..3....1..0..1..2....0..0..1..1....2..2..3..2
%K A208874 nonn
%O A208874 1,1
%A A208874 _R. H. Hardin_ Mar 02 2012