A207171 Number of 3 X n 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 1 0 1 vertically.

6, 36, 90, 261, 624, 1482, 3808, 9512, 23280, 58080, 144996, 359100, 891940, 2220008, 5514460, 13697376, 34051032, 84622140, 210256020, 522523332, 1298558624, 3226860476, 8018895456, 19927723520, 49521161364, 123062138780, 305817249300

Offset: 1

Author

R. H. Hardin, Feb 15 2012

Keywords

• nonn

Comments

Row 3 of A207169.

Examples

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

Links

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

Crossrefs

Cf. A207169.

Formula

Empirical: a(n) = a(n-1) + 9*a(n-3) + 2*a(n-4) + 2*a(n-5) - 12*a(n-6) - 8*a(n-7) + 8*a(n-9) for n>11.

Empirical g.f.: x*(6 + 30*x + 54*x^2 + 117*x^3 + 27*x^4 - 36*x^5 - 203*x^6 - 134*x^7 + 28*x^8 + 120*x^9 + 16*x^10) / (1 - x - 9*x^3 - 2*x^4 - 2*x^5 + 12*x^6 + 8*x^7 - 8*x^9). - Colin Barker, Mar 05 2018