A207929 Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 0 and 1 1 1 vertically.

6, 36, 72, 144, 360, 900, 2160, 5184, 12528, 30276, 73080, 176400, 425880, 1028196, 2482272, 5992704, 14467680, 34928100, 84323880, 203575824, 491475528, 1186526916, 2864529360, 6915585600, 16695700560, 40306986756, 97309674072

Offset: 1

Author

R. H. Hardin, Feb 21 2012

Keywords

• nonn

Comments

Row 3 of A207928.

Examples

			Some solutions for n=10:
..1..1..0..1..1..1..0..1..1..0....1..0..1..1..0..1..1..1..1..1
..0..0..1..1..0..0..1..1..0..0....1..0..0..1..1..0..1..1..0..0
..0..1..1..0..1..1..1..0..0..1....0..1..1..0..1..1..0..0..1..1
		

Links

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

Crossrefs

Cf. A207928.

Formula

Empirical: a(n) = 2*a(n-1) + 2*a(n-3) + a(n-4) for n>5.

Empirical g.f.: 6*x*(1 + 4*x - 2*x^3 - x^4) / ((1 + x^2)*(1 - 2*x - x^2)). - Colin Barker, Jun 26 2018