A221822 Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, without consecutive moves in the same direction.

6, 252, 6711, 190756, 5374720, 151592441, 4274867564, 120554575328, 3399703708400, 95873611077468, 2703690754567558, 76245627705373885, 2150170395738132532, 60636036995518426808, 1709970985328543058485

Offset: 1

Author

R. H. Hardin Jan 26 2013

Keywords

• nonn

Comments

Column 3 of A221824

Examples

			Some solutions for n=3
..1..3..1....0..1..0....0..2..1....1..1..1....1..0..0....2..0..1....1..1..1
..0..1..0....1..3..0....2..0..0....0..4..1....4..0..3....3..0..1....1..1..2
..0..2..1....0..3..1....1..2..1....1..0..0....0..0..1....0..2..0....0..0..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..180

Formula

Empirical: a(n) = 18*a(n-1) +312*a(n-2) -187*a(n-3) -13565*a(n-4) -20614*a(n-5) +158772*a(n-6) +381840*a(n-7) -1501245*a(n-8) -3110200*a(n-9) [phone]*a(n-10) -5218282*a(n-11) -30257641*a(n-12) [phone]*a(n-13) [phone]*a(n-14) -71002519*a(n-15) -62823023*a(n-16) [phone]*a(n-17) [phone]*a(n-18) -214821233*a(n-19) -158156578*a(n-20) [phone]*a(n-21) [phone]*a(n-22) -182698582*a(n-23) +171412*a(n-24) -59513311*a(n-25) [phone]*a(n-26) -136639431*a(n-27) [phone]*a(n-28) -84660389*a(n-29) [phone]*a(n-30) -6661260*a(n-31) +3867558*a(n-32) -132564*a(n-33) +150444*a(n-34) -5832*a(n-35)