A235889 Number of (n+1) X (4+1) 0..3 arrays with the minimum plus the upper median equal to the lower median plus the maximum in every 2 X 2 subblock.

1216, 1624, 2536, 4744, 10696, 28744, 89416, 309064, 1141576, 4379464, 17146696, 67846984, 269910856, 1076691784, 4300866376, 17191666504, 68743070536, 274925093704, 1099606000456, 4398235255624, 17592563532616, 70369499153224

Offset

1,1

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3).

Conjectures from Colin Barker, Oct 20 2018: (Start)

G.f.: 8*x*(152 - 861*x + 1024*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).

a(n) = 4*(210 + 45*2^n + 4^n).

(End)

Example

Some solutions for n=4:
..1..1..3..1..1....0..0..0..0..0....2..1..2..1..1....2..0..3..2..2
..3..3..1..3..3....3..3..3..3..3....2..1..2..1..1....2..0..3..2..2
..3..3..1..3..3....2..2..2..2..2....2..1..2..1..1....2..0..3..2..2
..1..1..3..1..1....3..3..3..3..3....1..2..1..2..2....2..0..3..2..2
..1..1..3..1..1....1..1..1..1..1....1..2..1..2..2....2..0..3..2..2

Crossrefs

Column 4 of A235893.

Sequence in context: A346207 A068783 A331625 * A321062 A059287 A225759

Adjacent sequences: A235886 A235887 A235888 * A235890 A235891 A235892

Keyword

nonn

Author

R. H. Hardin, Jan 16 2014

Status

approved