A229514 Number of n X 1 0..2 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..2 array without adjacent equal elements in the latter.

3, 7, 17, 39, 91, 211, 491, 1141, 2653, 6167, 14337, 33329, 77481, 180121, 418731, 973431, 2262953, 5260727, 12229707, 28430619, 66093171, 153647981, 357188221, 830361871, 1930357153, 4487535937, 10432255377, 24252051409, 56379179411

Offset

1,1

Links

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

Formula

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

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

Example

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

Crossrefs

Column 1 of A229521.

Sequence in context: A157029 A191825 A342600 * A077927 A005197 A147142

Adjacent sequences: A229511 A229512 A229513 * A229515 A229516 A229517

Keyword

nonn

Author

R. H. Hardin, Sep 25 2013

Status

approved