A242578 Number of length n+3 0..2 arrays with no four elements in a row with pattern aabb (with a!=b) and new values 0..2 introduced in 0..2 order.

13, 35, 97, 271, 757, 2115, 5913, 16535, 46237, 129291, 361537, 1010975, 2827013, 7905235, 22105577, 61814311, 172852717, 483351835, 1351607313, 3779529135, 10568780117, 29553711331, 82641690297, 231092768695, 646209770813

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) - 5*a(n-2) + 6*a(n-3) - 4*a(n-4).

Empirical g.f.: x*(13 - 17*x + 22*x^2 - 20*x^3) / ((1 - x)*(1 - 3*x + 2*x^2 - 4*x^3)). - Colin Barker, Nov 01 2018

Example

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

Crossrefs

Column 2 of A242584.

Sequence in context: A227986 A228024 A243383 * A192145 A221592 A135172

Adjacent sequences: A242575 A242576 A242577 * A242579 A242580 A242581

Keyword

nonn

Author

R. H. Hardin, May 17 2014

Status

approved