A251204 - OEIS

%I #8 Nov 27 2018 09:02:01

%S 180,1246,8870,65040,489772,3775022,29664576,236740252,1912108322,

%T 15584536740,127880485540,1054537633526,8727275684760,72413361371620,

%U 601955189383922,5010545177519292,41746084890460636,348047155647060662

%N Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock summing to a nonzero multiple of 2.

%H R. H. Hardin, <a href="/A251204/b251204.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 18*a(n-1) - 90*a(n-2) + 7*a(n-3) + 576*a(n-4) + 210*a(n-5) - 180*a(n-6).

%F Empirical g.f.: 2*x*(90 - 997*x + 1321*x^2 + 8130*x^3 + 2475*x^4 - 2430*x^5) / ((1 - 6*x)*(1 - 5*x - 5*x^2)*(1 - 7*x - 12*x^2 + 6*x^3)). - _Colin Barker_, Nov 27 2018

%e Some solutions for n=4:

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

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

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

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

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

%Y Column 2 of A251210.

%K nonn

%O 1,1

%A _R. H. Hardin_, Nov 30 2014