A207909 Number of 4Xn 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 0 and 0 1 1 vertically.

9, 81, 261, 841, 4089, 19881, 80511, 326041, 1428071, 6255001, 26473085, 112042225, 481310535, 2067611841, 8824602441, 37663553041, 161202941369, 689961148321, 2949462033565, 12608429197225, 53927628353015, 230654354661481

Offset: 1

Author

R. H. Hardin Feb 21 2012

Keywords

• nonn

Comments

Row 4 of A207908

Examples

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

Links

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

Formula

Empirical: a(n) = 3*a(n-1) +15*a(n-3) +67*a(n-4) -103*a(n-5) -69*a(n-6) -157*a(n-7) -735*a(n-8) +867*a(n-9) +665*a(n-10) +273*a(n-11) +2309*a(n-12) -2157*a(n-13) -1104*a(n-14) -82*a(n-15) -2401*a(n-16) +1858*a(n-17) +342*a(n-18) +28*a(n-19) +644*a(n-20) -456*a(n-21) -32*a(n-22) -48*a(n-24) +32*a(n-25)