A235880 Number of (n+1) X (4+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.

339, 537, 951, 1833, 3759, 8097, 18231, 42873, 105279, 269457, 715911, 1963113, 5520399, 15823617, 45995991, 135038553, 399217119, 1185854577, 3533970471, 10554725193, 31569803439, 94520666337, 283184511351, 848798559033

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*(113 - 499*x + 486*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).

a(n) = 3*(50 + 15*2^(1+n) + 3^n).

(End)

Example

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

Crossrefs

Column 4 of A235884.

Sequence in context: A035750 A186043 A107546 * A158000 A252447 A252441

Adjacent sequences: A235877 A235878 A235879 * A235881 A235882 A235883

Keyword

nonn

Author

R. H. Hardin, Jan 16 2014

Status

approved