A235881 Number of (n+1) X (5+1) 0..2 arrays with the minimum plus the upper median equal to the lower median plus the maximum in every 2 X 2 subblock.

921, 1311, 2109, 3759, 7221, 14631, 30909, 67839, 154821, 368151, 912909, 2356719, 6307221, 17396871, 49142109, 141330399, 411800421, 1211020791, 3584302509, 10655388879, 31771130421, 94923319911, 283989818109, 850409172159

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) -11*a(n-2) +6*a(n-3).

Conjectures from Colin Barker, Oct 19 2018: (Start)

G.f.: 3*x*(307 - 1405*x + 1458*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).

a(n) = 3*(180 + 31*2^(1+n) + 3^n).

(End)

Example

Some solutions for n=5:
..2..1..1..1..1..2....2..1..2..1..2..2....1..1..0..1..0..1....1..1..1..1..1..1
..2..1..1..1..1..2....2..1..2..1..2..2....0..0..1..0..1..0....0..0..0..0..0..0
..2..1..1..1..1..2....1..2..1..2..1..1....1..1..0..1..0..1....2..2..2..2..2..2
..1..2..2..2..2..1....1..2..1..2..1..1....0..0..1..0..1..0....1..1..1..1..1..1
..2..1..1..1..1..2....1..2..1..2..1..1....1..1..0..1..0..1....2..2..2..2..2..2
..2..1..1..1..1..2....1..2..1..2..1..1....1..1..0..1..0..1....1..1..1..1..1..1

Crossrefs

Column 5 of A235884.

Sequence in context: A332191 A068163 A289794 * A051984 A232732 A228673

Adjacent sequences: A235878 A235879 A235880 * A235882 A235883 A235884

Keyword

nonn

Author

R. H. Hardin, Jan 16 2014

Status

approved