cp's OEIS Frontend

A221777 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, without move-in move-out left turns.

%I A221777 #9 Mar 14 2018 12:20:55
%S A221777 3,25,184,1367,10179,75782,564169,4200043,31267890,232778781,
%T A221777 1732958641,12901286112,96045675555,715027301353,5323134422488,
%U A221777 39628920498935,295023799000179,2196351575583206,16351088488165993,121728277803994939
%N A221777 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, without move-in move-out left turns.
%C A221777 Column 2 of A221780.
%H A221777 R. H. Hardin, <a href="/A221777/b221777.txt">Table of n, a(n) for n = 1..210</a>
%F A221777 Empirical: a(n) = 8*a(n-1) - 5*a(n-2) + 7*a(n-3) - 4*a(n-4) - a(n-5).
%F A221777 Empirical g.f.: x*(3 + x - x^2 - x^3) / ((1 + x^2)*(1 - 8*x + 4*x^2 + x^3)). - _Colin Barker_, Mar 14 2018
%e A221777 Some solutions for n=3:
%e A221777 ..0..2....0..1....1..2....0..0....0..2....1..1....2..0....2..0....1..1....0..1
%e A221777 ..1..3....1..2....1..2....2..1....2..2....2..2....1..2....1..2....0..0....0..3
%e A221777 ..0..0....0..2....0..0....3..0....0..0....0..0....0..1....1..0....2..2....2..0
%Y A221777 Cf. A221780.
%K A221777 nonn
%O A221777 1,1
%A A221777 _R. H. Hardin_, Jan 25 2013