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

1,1

Links

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

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

Example

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

Crossrefs

Column 1 of A229320.

Sequence in context: A352456 A034459 A120747 * A055099 A335921 A372874

Adjacent sequences: A229311 A229312 A229313 * A229315 A229316 A229317

Keyword

nonn

Author

R. H. Hardin, Sep 19 2013

Status

approved