A236323 Number of (n+1) X (1+1) 0..1 arrays colored with the sum of the upper and lower median values of each 2 X 2 subblock.

16, 32, 60, 120, 252, 496, 972, 1960, 3980, 7872, 15676, 31512, 63260, 125840, 251692, 504456, 1009452, 2014560, 4031900, 8069112, 16136636, 32249392, 64530060, 129075560, 258121932, 516130816, 1032513532, 2064979160, 4129750620

Offset

1,1

Links

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

Formula

Empirical: a(n) = a(n-2) + 2*a(n-3) + 8*a(n-4).

Empirical g.f.: 4*x*(4 + 8*x + 11*x^2 + 14*x^3) / ((1 - 2*x)*(1 + 2*x + 3*x^2 + 4*x^3)). - Colin Barker, Oct 21 2018

Example

Some solutions for n=5:
..1..1....1..1....1..0....1..1....1..1....0..0....1..1....0..0....0..0....1..1
..0..1....0..1....0..1....0..1....0..1....0..0....0..1....0..1....0..1....1..1
..0..1....0..0....0..0....1..0....1..0....1..1....0..1....0..1....0..1....0..0
..0..0....1..1....1..1....1..1....0..0....1..0....1..1....1..1....1..1....1..0
..1..1....1..0....0..1....0..0....1..1....1..0....0..0....0..0....0..0....1..0
..1..0....0..1....0..1....1..0....1..1....0..0....1..0....0..0....1..0....1..1

Crossrefs

Sequence in context: A224544 A255994 A204645 * A018923 A264901 A339840

Adjacent sequences: A236320 A236321 A236322 * A236324 A236325 A236326

Keyword

nonn

Author

R. H. Hardin, Jan 22 2014

Status

approved