A221769 - OEIS

%I #8 Aug 10 2018 17:34:17

%S 3,27,240,2127,18828,166581,1473549,13033908,115285587,1019699649,

%T 9019211256,79774585647,705603080553,6241031204616,55201672045839,

%U 488256584905473,4318609990477032,38197932848425719,337859190101460441

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

%C Column 2 of A221773.

%H R. H. Hardin, <a href="/A221769/b221769.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 15*a(n-1) - 67*a(n-2) + 120*a(n-3) - 80*a(n-4) + 10*a(n-5).

%F Empirical g.f.: 3*x*(1 - x)*(1 - 5*x + 7*x^2 - x^3) / (1 - 15*x + 67*x^2 - 120*x^3 + 80*x^4 - 10*x^5). - _Colin Barker_, Aug 10 2018

%e Some solutions for n=3:

%e ..1..0....1..0....0..1....2..1....0..2....0..1....0..1....2..1....0..3....1..1

%e ..0..3....2..2....2..2....2..0....1..0....0..3....2..1....0..0....1..1....1..2

%e ..1..1....0..1....0..1....0..1....2..1....2..0....1..1....0..3....1..0....0..1

%Y Cf. A221773.

%K nonn

%O 1,1

%A _R. H. Hardin_, Jan 25 2013