A221939 Number of 3Xn arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out straight through or left turns.

1, 91, 1599, 36467, 799632, 17595404, 387146025, 8517616158, 187399250327, 4123030670649, 90712135220235, 1995786856338823, 43909951229853113, 966076992787974879, 21254971544597958477, 467637484141672483673

Offset: 1

Author

R. H. Hardin Feb 01 2013

Keywords

• nonn

Comments

Row 3 of A221937

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..98

Formula

Empirical: a(n) = 6*a(n-1) +286*a(n-2) +1731*a(n-3) -3366*a(n-4) -58755*a(n-5) -73158*a(n-6) +744580*a(n-7) +1606773*a(n-8) -5847271*a(n-9) -13299665*a(n-10) [phone]*a(n-11) [phone]*a(n-12) -168213873*a(n-13) -99886051*a(n-14) [phone]*a(n-15) -127805646*a(n-16) -951724652*a(n-17) [phone]*a(n-18) [phone]*a(n-19) -1511277493*a(n-20) [phone]*a(n-21) [phone]*a(n-22) -708567632*a(n-23) -119679569*a(n-24) [phone]*a(n-25) -92576435*a(n-26) -25624476*a(n-27) [phone]*a(n-28) -1254086*a(n-29) -1085212*a(n-30) +391330*a(n-31) -46391*a(n-32) -25190*a(n-33) +7306*a(n-34) +873*a(n-35) -236*a(n-36) -12*a(n-37) for n>38