A235886 Number of (n+1) X (1+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.

40, 112, 352, 1216, 4480, 17152, 67072, 265216, 1054720, 4206592, 16801792, 67158016, 268533760, 1073938432, 4295360512, 17180655616, 68721049600, 274881052672, 1099517919232, 4398059094016, 17592211210240, 70368794509312

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 8*a(n-2).

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

G.f.: 8*x*(5 - 16*x) / ((1 - 2*x)*(1 - 4*x)).

a(n) = 2^(2+n) * (3+2^n).

(End)

Example

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

Crossrefs

Column 1 of A235893.

Sequence in context: A235893 A192791 A345970 * A261191 A260601 A234921

Adjacent sequences: A235883 A235884 A235885 * A235887 A235888 A235889

Keyword

nonn

Author

R. H. Hardin, Jan 16 2014

Status

approved