A248456 Number of length n+2 0..3 arrays with no three consecutive terms having the sum of any two elements equal to twice the third.

48, 148, 460, 1436, 4488, 14040, 43940, 137532, 430508, 1347652, 4218704, 13206360, 41341772, 129418260, 405137308, 1268262348, 3970233208, 12428621208, 38907193300, 121797075276, 381279818252, 1193577924020, 3736437636672

Offset

1,1

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 3*a(n-2) + 4*a(n-3) - 3*a(n-4) - 12*a(n-5) - 4*a(n-6).

Empirical g.f.: 4*x*(12 + 13*x + 5*x^2 - 30*x^3 - 53*x^4 - 16*x^5) / (1 - 2*x - 3*x^2 - 4*x^3 + 3*x^4 + 12*x^5 + 4*x^6). - Colin Barker, Nov 08 2018

Example

Some solutions for n=6:
..0....0....0....1....0....2....2....2....2....3....3....1....2....2....0....2
..3....1....3....1....3....3....1....0....3....0....3....1....2....2....3....2
..1....3....1....3....3....0....1....3....3....3....1....0....3....0....2....1
..3....3....3....0....1....0....3....0....2....0....1....1....0....2....0....1
..1....1....0....0....0....3....1....2....3....1....2....0....3....3....0....2
..3....0....3....3....3....3....3....3....3....0....1....0....0....0....2....2
..1....1....0....0....1....0....1....0....2....3....2....2....0....3....0....1
..1....3....2....1....0....0....3....0....2....0....2....2....1....0....2....1

Crossrefs

Column 3 of A248461.

Sequence in context: A039496 A044380 A044761 * A370126 A346293 A244178

Adjacent sequences: A248453 A248454 A248455 * A248457 A248458 A248459

Keyword

nonn

Author

R. H. Hardin, Oct 06 2014

Status

approved