A207694 Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 1 1 1 vertically.

6, 36, 60, 100, 240, 576, 1296, 2916, 6804, 15876, 36288, 82944, 191808, 443556, 1018980, 2340900, 5397840, 12446784, 28640304, 65901924, 151822836, 349764804, 805233312, 1853819136, 4269519072, 9833102244, 22641659460, 52134588900

Offset: 1

Author

R. H. Hardin, Feb 19 2012

Keywords

• nonn

Comments

Row 3 of A207693.

Examples

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

Links

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

Crossrefs

Cf. A207693.

Formula

Empirical: a(n) = a(n-1) + 3*a(n-3) + 9*a(n-4) for n>7.

Empirical g.f.: 2*x*(3 + 15*x + 12*x^2 + 11*x^3 - 11*x^4 - 84*x^5 - 60*x^6) / ((1 + 3*x^2)*(1 - x - 3*x^2)). - Colin Barker, Mar 05 2018