A185514 Number of (n+1) X 3 0..2 arrays with every 2 X 2 subblock singular.

143, 1489, 12361, 115979, 1058503, 9856209, 91539073, 853020411, 7948563615, 74110312433, 691029158489, 6444134240459, 60095780277207, 560446106259121, 5226693550531025, 48744151344694907, 454588941498687343

Offset: 1

Author

R. H. Hardin, Jan 29 2011

Keywords

• nonn

Comments

Column 2 of A185521.

Examples

			Some solutions for 5 X 3:
..0..0..2....2..0..1....0..0..2....1..0..2....2..0..0....2..0..0....0..1..2
..0..0..1....2..0..2....2..0..2....1..0..1....1..0..1....2..0..2....0..0..0
..0..0..1....2..0..2....0..0..0....1..0..0....1..0..1....2..0..0....1..2..2
..1..0..0....1..0..1....0..0..2....2..0..1....0..0..0....0..0..1....0..0..0
..1..0..2....0..0..2....0..0..1....1..0..0....1..1..2....0..0..2....1..1..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A185521.

Formula

Empirical: a(n) = 12*a(n-1) - 11*a(n-2) - 154*a(n-3) + 224*a(n-4).

Empirical g.f.: x*(143 - 227*x - 3934*x^2 + 6048*x^3) / (1 - 12*x + 11*x^2 + 154*x^3 - 224*x^4). - Colin Barker, Apr 16 2018