cp's OEIS Frontend

A220997 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor.

%I A220997 #8 Feb 23 2018 11:28:43
%S A220997 3,31,306,2989,29135,283872,2765627,26943707,262494146,2557299561,
%T A220997 24914003827,242719929760,2364652602239,23037176752223,
%U A220997 224435298485050,2186518067974709,21301735038155095,207528088736659200
%N A220997 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor.
%C A220997 Column 2 of A221001.
%H A220997 R. H. Hardin, <a href="/A220997/b220997.txt">Table of n, a(n) for n = 1..210</a>
%F A220997 Empirical: a(n) = 11*a(n-1) - 11*a(n-2) - 12*a(n-3) - 2*a(n-4).
%F A220997 Empirical g.f.: x*(3 - 2*x - 2*x^2) / (1 - 11*x + 11*x^2 + 12*x^3 + 2*x^4). - _Colin Barker_, Feb 23 2018
%e A220997 Some solutions for n=3:
%e A220997 ..2..1....3..0....1..1....0..2....0..2....0..1....1..1....3..0....0..1....0..1
%e A220997 ..1..2....0..1....1..1....1..1....1..3....2..0....3..0....0..1....1..3....3..1
%e A220997 ..0..0....1..1....0..2....1..1....0..0....1..2....1..0....2..0....0..1....1..0
%Y A220997 Cf. A221001.
%K A220997 nonn
%O A220997 1,1
%A A220997 _R. H. Hardin_, Dec 28 2012