A228980 Number of n X 2 0..1 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 3 0..1 array.

4, 16, 64, 252, 992, 3900, 15328, 60228, 236624, 929580, 3651712, 14344836, 56349296, 221349132, 869490976, 3415475172, 13416415184, 52701313836, 207017071552, 813187592388, 3194296661552, 12547572276300, 49288333901920

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 7*a(n-2) - 6*a(n-3) + 6*a(n-4).

Empirical g.f.: 4*x*(1 - 2*x - x^2 + x^3) / (1 - 6*x + 7*x^2 + 6*x^3 - 6*x^4). - Colin Barker, Sep 13 2018

Example

Some solutions for n=4:
..0..1....1..0....0..1....0..1....1..0....1..0....1..1....1..1....0..1....1..0
..1..0....1..1....0..1....0..0....1..1....1..0....0..1....0..0....0..0....1..1
..0..0....0..1....0..0....1..1....1..1....1..0....1..0....1..1....0..0....0..0
..1..0....0..1....0..1....1..1....1..0....1..0....1..1....1..0....0..1....1..0

Crossrefs

Column 2 of A228986.

Sequence in context: A307945 A370143 A269771 * A188714 A005755 A269651

Adjacent sequences: A228977 A228978 A228979 * A228981 A228982 A228983

Keyword

nonn

Author

R. H. Hardin, Sep 10 2013

Status

approved