A235879 Number of (n+1) X (3+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.

129, 231, 453, 951, 2109, 4911, 11973, 30471, 80589, 220191, 617493, 1766391, 5127069, 15037071, 44423013, 131892711, 392925549, 1173271551, 3508804533, 10504393431, 31469140029, 94319339631, 282781858053, 847993252551

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*(43 - 181*x + 162*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).

a(n) = 3*(12 + 7*2^(1+n) + 3^n).

(End)

Example

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

Crossrefs

Column 3 of A235884.

Sequence in context: A185347 A034072 A178228 * A157951 A043383 A250814

Adjacent sequences: A235876 A235877 A235878 * A235880 A235881 A235882

Keyword

nonn

Author

R. H. Hardin, Jan 16 2014

Status

approved