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A183519 Number of nX2 0..2 arrays with each element equal to either the sum mod 3 of its horizontal and vertical neighbors or the sum mod 3 of its diagonal and antidiagonal neighbors.

%I A183519 #7 Jul 22 2025 09:03:25
%S A183519 3,9,31,95,309,911,2803,8673,26619,81959,252477,777327,2393627,
%T A183519 7371657,22698115,69895583,215235669,662786215,2040959827,6284869089,
%U A183519 19353386043,59596135287,183518286189,565119695167,1740209766219,5358741068409
%N A183519 Number of nX2 0..2 arrays with each element equal to either the sum mod 3 of its horizontal and vertical neighbors or the sum mod 3 of its diagonal and antidiagonal neighbors.
%C A183519 Column 2 of A183526
%H A183519 R. H. Hardin, <a href="/A183519/b183519.txt">Table of n, a(n) for n = 1..200</a>
%F A183519 Empirical: a(n)=3*a(n-1)+6*a(n-3)-16*a(n-4)+7*a(n-6)-25*a(n-7)-44*a(n-9)+102*a(n-10)-184*a(n-12)+520*a(n-13)+320*a(n-15)-720*a(n-16)+640*a(n-18)-1600*a(n-19)
%e A183519 Some solutions for 3X2
%e A183519 ..1..2....0..2....2..1....2..0....0..2....2..2....1..0....1..0....0..1....1..2
%e A183519 ..0..1....1..2....1..2....0..2....1..2....0..0....1..2....1..2....2..1....2..1
%e A183519 ..1..2....2..1....0..2....0..0....0..2....1..1....1..0....2..1....1..2....2..0
%K A183519 nonn
%O A183519 1,1
%A A183519 _R. H. Hardin_ Jan 05 2011