A204679 Number of n X 2 0..3 arrays with no occurrence of three equal elements in a row horizontally, vertically, diagonally or antidiagonally, and new values 0..3 introduced in row major order.

2, 15, 159, 2191, 31168, 447343, 6427791, 92387812, 1327953799, 19087798375, 274365294336, 3943689122935, 56686048473223, 814797524429284, 11711788424726319, 168343648648695295, 2419748633865949120

Offset: 1

Author

R. H. Hardin, Jan 18 2012

Keywords

• nonn

Comments

Column 2 of A204685.

Examples

			Some solutions for n=5:
..0..1....0..0....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..0
..1..0....1..0....1..0....0..1....0..0....0..0....0..0....0..0....0..1....0..0
..0..0....0..1....0..0....1..2....1..2....1..1....1..1....1..2....1..0....1..1
..0..1....1..0....2..1....0..1....1..3....2..3....0..1....2..1....1..0....1..2
..1..0....0..1....0..2....0..0....2..0....3..0....1..2....1..0....2..3....2..0
		

Links

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

Crossrefs

Cf. A204685.

Formula

Empirical: a(n) = 14*a(n-1) +14*a(n-2) -124*a(n-3) -6*a(n-4) +90*a(n-5) -27*a(n-6) for n>8.

Empirical g.f.: x*(2 - 13*x - 79*x^2 + 3*x^3 + 140*x^4 - 57*x^5 - 21*x^6 + 9*x^7) / ((1 + x)*(1 + 3*x)*(1 - 3*x + x^2)*(1 - 15*x + 9*x^2)). - Colin Barker, Feb 23 2018