A229314 Number of n X 1 0..3 arrays of the median of the corresponding element, the element to the east and the element to the south in a larger (n+1) X 2 0..3 array without adjacent equal elements in the latter.

4, 14, 50, 176, 622, 2196, 7756, 27390, 96730, 341606, 1206400, 4260462, 15046040, 53135856, 187651986, 662702554, 2340367858, 8265128408, 29188722358, 103081461140, 364037435444, 1285616763070, 4540221143674, 16034022443998

Offset: 1

Author

R. H. Hardin, Sep 19 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 1 of A229320.

Formula

Empirical: a(n) = 3*a(n-1) + 2*a(n-2) - a(n-3) + 2*a(n-4).

Empirical g.f.: 2*x*(1 + x)*(2 - x + x^2) / (1 - 3*x - 2*x^2 + x^3 - 2*x^4). - Colin Barker, Sep 14 2018