A184369 1/3 the number of (n+1) X 3 0..2 arrays with every 2 X 2 subblock having at least two equal elements connected horizontally or vertically.

153, 2755, 49235, 880781, 15754461, 281803871, 5040682279, 90163722073, 1612776998193, 28848073268443, 516011408652059, 9230001997285733, 165098940527912805, 2953158641948611223, 52823754874667184367

Offset: 1

Author

R. H. Hardin, Jan 12 2011

Keywords

• nonn

Comments

Column 2 of A184376.

Examples

			Some solutions for 5 X 3 with a(1,1)=0:
..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
..1..0..2....1..2..2....0..1..0....0..2..2....1..1..1....0..2..0....1..1..0
..1..2..2....0..2..0....1..1..1....1..1..2....1..2..0....1..2..0....1..0..0
..1..2..2....1..1..0....2..1..2....2..1..2....1..1..1....1..2..0....2..2..2
..1..1..1....2..2..2....0..1..0....0..0..0....0..2..0....0..2..1....0..2..0
		

Links

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

Crossrefs

Cf. A184376.

Formula

Empirical: a(n) = 17*a(n-1) + 19*a(n-2) - 57*a(n-3) + 18*a(n-4).

Empirical g.f.: x*(153 + 154*x - 507*x^2 + 162*x^3) / (1 - 17*x - 19*x^2 + 57*x^3 - 18*x^4). - Colin Barker, Feb 27 2018