A208009 Number of n X 4 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 0 1 1 vertically.

9, 81, 261, 841, 1943, 4489, 8643, 16641, 28509, 48841, 77129, 121801, 181131, 269361, 382503, 543169, 743633, 1018081, 1353069, 1798281, 2331999, 3024121, 3841451, 4879681, 6090213, 7601049, 9343473, 11485321, 13932179, 16900321

Offset: 1

Author

R. H. Hardin, Feb 22 2012

Keywords

• nonn

Comments

Column 4 of A208013.

Examples

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

Links

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

Crossrefs

Cf. A208013.

Formula

Empirical: a(n) = 2*a(n-1) + 4*a(n-2) - 10*a(n-3) - 5*a(n-4) + 20*a(n-5) - 20*a(n-7) + 5*a(n-8) + 10*a(n-9) - 4*a(n-10) - 2*a(n-11) + a(n-12).

Empirical g.f.: x*(9 + 63*x + 63*x^2 + 85*x^3 + 72*x^4 + 74*x^5 - 12*x^6 - 6*x^7 + 15*x^8 - x^9 - 3*x^10 + x^11) / ((1 - x)^7*(1 + x)^5). - Colin Barker, Jun 26 2018