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A185900 1/8 the number of nX3 0..7 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.

%I A185900 #9 Jul 22 2025 10:07:20
%S A185900 1,196,7854,546280,28967421,1748982326,98953708266,5781843976125,
%T A185900 332434487651623,19267808077145684,1112287426359828719,
%U A185900 64338491237732078416,3717840477156798616939,214944959102538319886245
%N A185900 1/8 the number of nX3 0..7 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.
%C A185900 Column 3 of A185903
%H A185900 R. H. Hardin, <a href="/A185900/b185900.txt">Table of n, a(n) for n = 1..155</a>
%F A185900 Empirical: a(n)=32*a(n-1)+1746*a(n-2)-10029*a(n-3)-277751*a(n-4)+323380*a(n-5)+6665171*a(n-6)-1880040*a(n-7)-2212279*a(n-8)-295754815*a(n-9)+974325088*a(n-10)-1138247283*a(n-11)-3413532399*a(n-12)-6260334885*a(n-13)+43564745112*a(n-14)+67448015978*a(n-15)-317297809157*a(n-16)+933625841547*a(n-17)+1754321298765*a(n-18)-4758109448687*a(n-19)-10555269100243*a(n-20)-10151918327418*a(n-21)-9040337868996*a(n-22)-20928026247912*a(n-23)
%e A185900 Some solutions for 5X3 with a(1,1)=0
%e A185900 ..0..4..0....0..4..0....0..4..4....0..4..0....0..4..0....0..0..0....0..0..0
%e A185900 ..0..4..0....0..4..0....0..0..4....0..4..0....0..4..0....4..4..4....0..4..4
%e A185900 ..2..4..4....2..2..2....2..2..4....4..6..6....2..2..2....6..0..0....0..2..2
%e A185900 ..2..2..0....6..5..6....4..4..4....4..3..5....0..4..6....6..7..7....6..6..6
%e A185900 ..0..0..0....6..5..6....2..2..2....4..3..5....0..4..6....6..2..2....2..2..6
%K A185900 nonn
%O A185900 1,2
%A A185900 _R. H. Hardin_ Feb 06 2011