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%I A197539 #9 May 13 2018 06:04:14
%S A197539 1,5,8,19,28,58,119,219,395,776,1529,2826,5300,10299,19763,37051,
%T A197539 70380,135411,257788,487412,929135,1776855,3377845,6414026,12229725,
%U A197539 23320560,44346952,84364697,160777089,306229857,582642042,1109154715,2112783972
%N A197539 Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,2,1,1,1 for x=0,1,2,3,4.
%C A197539 Every 0 is next to 0 2's, every 1 is next to 1 2's, every 2 is next to 2 1's, every 3 is next to 3 1's, every 4 is next to 4 1's.
%C A197539 Column 2 of A197545.
%H A197539 R. H. Hardin, <a href="/A197539/b197539.txt">Table of n, a(n) for n = 1..200</a>
%F A197539 Empirical: a(n) = a(n-1) +2*a(n-3) +4*a(n-4) -3*a(n-5) -a(n-6) +3*a(n-7) -2*a(n-8).
%F A197539 Empirical g.f.: x*(1 + 4*x + 3*x^2 + 9*x^3 - 5*x^4 - 3*x^5 + 7*x^6 - 6*x^7) / (1 - x - 2*x^3 - 4*x^4 + 3*x^5 + x^6 - 3*x^7 + 2*x^8). - _Colin Barker_, May 13 2018
%e A197539 Some solutions for n=4:
%e A197539 ..2..1....1..2....2..1....1..0....0..0....2..1....1..2....1..1....1..2....2..1
%e A197539 ..1..0....0..1....1..0....2..1....0..0....1..0....3..1....2..2....0..1....1..3
%e A197539 ..3..1....1..0....1..0....2..1....0..1....0..1....1..3....1..1....1..3....0..1
%e A197539 ..1..2....2..1....2..1....1..0....1..2....1..2....2..1....0..0....2..1....1..2
%Y A197539 Cf. A197545.
%K A197539 nonn
%O A197539 1,2
%A A197539 _R. H. Hardin_, Oct 16 2011

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