A222439 Number of n X 3 0..3 arrays with entries increasing mod 4 by 0, 1 or 2 rightwards and downwards, starting with upper left zero.

9, 147, 2403, 39285, 642249, 10499787, 171655443, 2806303725, 45878770089, 750047661027, 12262131106083, 200467073061765, 3277329775247529, 53579324981787867, 875939945740498323, 14320277248820697405

Offset: 1

Author

R. H. Hardin, Feb 20 2013

Keywords

• nonn

Comments

Column 3 of A222444.

Examples

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

Links

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

Crossrefs

Cf. A222444.

Formula

Empirical: a(n) = 18*a(n-1) - 27*a(n-2).

Empirical g.f.: 3*x*(3 - 5*x) / (1 - 18*x + 27*x^2). - Colin Barker, Mar 15 2018