A235891 Number of (n+1) X (6+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.

17152, 18712, 21928, 28744, 43912, 80392, 177928, 471304, 1451272, 4984072, 18341128, 70221064, 274644232, 1086143752, 4319755528, 17229430024, 68818582792, 275076103432, 1099908005128, 4398839250184, 17593771506952

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..147

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*(2144 - 12669*x + 16384*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).

a(n) = 4*(3906 + 189*2^n + 4^n).

(End)

Example

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

Crossrefs

Column 6 of A235893.

Sequence in context: A121669 A247697 A218247 * A251207 A233993 A043621

Adjacent sequences: A235888 A235889 A235890 * A235892 A235893 A235894

Keyword

nonn

Author

R. H. Hardin, Jan 16 2014

Status

approved