A208841 Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 1 and 1 1 0 vertically.

9, 81, 171, 855, 2421, 9801, 31419, 116919, 394965, 1419849, 4902939, 17375031, 60551541, 213310665, 746231931, 2622329271, 9188418069, 32255749449, 113096449755, 396852637239, 1391845926069, 4883081614281, 17127968887611

Offset: 1

Author

R. H. Hardin, Mar 01 2012

Keywords

• nonn

Comments

Row 4 of A208840.

Examples

			Some solutions for n=4:
..1..1..1..1....0..1..1..1....0..1..1..0....0..1..1..0....1..0..1..1
..0..1..0..1....0..1..0..1....0..1..1..1....1..1..0..0....0..1..1..0
..1..1..1..1....0..1..0..1....1..1..1..0....0..1..0..1....1..0..1..1
..0..1..0..1....0..1..1..1....0..1..1..1....0..1..1..0....0..1..1..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A208840.

Formula

Empirical: a(n) = 2*a(n-1) +7*a(n-2) -6*a(n-3).