A251276 Number of (n+1) X (1+1) 0..3 arrays with no 2 X 2 subblock having its maximum diagonal element less than its minimum antidiagonal element.

230, 3264, 46244, 655040, 9278296, 131421696, 1861511440, 26367218944, 373476205664, 5290071598080, 74930764222016, 1061350366002176, 15033405986262400, 212939386264141824, 3016161624583446784

Offset

1,1

Links

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

Formula

Empirical: a(n) = 16*a(n-1) - 26*a(n-2).

Conjectures from Colin Barker, Nov 27 2018: (Start)

G.f.: 2*x*(115 - 208*x) / (1 - 16*x + 26*x^2).

a(n) = ((8-sqrt(38))^n*(-51+8*sqrt(38)) + (8+sqrt(38))^n*(51+8*sqrt(38))) / sqrt(38).

(End)

Example

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

Crossrefs

Column 1 of A251283.

Sequence in context: A211716 A251445 A251283 * A194490 A232379 A333136

Adjacent sequences: A251273 A251274 A251275 * A251277 A251278 A251279

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved