cp's OEIS Frontend

A199641 Number of n X 2 0..2 arrays with values 0..2 introduced in row major order and each element equal to one or two horizontal and vertical neighbors.

%I A199641 #8 May 16 2018 06:43:23
%S A199641 1,3,13,60,288,1384,6628,31772,152304,730036,3499340,16773680,
%T A199641 80402532,385399644,1847365808,8855120468,42445929772,203459338800,
%U A199641 975257291396,4674775757500,22407962058928,107409807372276,514855687878924
%N A199641 Number of n X 2 0..2 arrays with values 0..2 introduced in row major order and each element equal to one or two horizontal and vertical neighbors.
%C A199641 Column 2 of A199647.
%H A199641 R. H. Hardin, <a href="/A199641/b199641.txt">Table of n, a(n) for n = 1..200</a>
%F A199641 Empirical: a(n) = 3*a(n-1) +7*a(n-2) +8*a(n-3) -8*a(n-5) for n>7.
%F A199641 Empirical g.f.: x*(1 - 3*x^2 - 8*x^3 - 7*x^4 + 4*x^5 + 4*x^6) / (1 - 3*x - 7*x^2 - 8*x^3 + 8*x^5). - _Colin Barker_, May 16 2018
%e A199641 Some solutions for n=3:
%e A199641 ..0..1....0..0....0..0....0..1....0..0....0..0....0..0....0..1....0..0....0..0
%e A199641 ..0..1....0..0....1..0....0..1....1..1....1..1....1..0....0..1....0..1....0..1
%e A199641 ..0..1....1..1....1..0....2..2....1..1....2..2....1..1....1..1....0..1....1..1
%Y A199641 Cf. A199647.
%K A199641 nonn
%O A199641 1,2
%A A199641 _R. H. Hardin_, Nov 08 2011