A248457 Number of length n+2 0..4 arrays with no three consecutive terms having the sum of any two elements equal to twice the third.

96, 380, 1512, 6040, 24160, 96736, 387488, 1552448, 6220480, 24926080, 99883840, 400260160, 1603955712, 6427525312, 25757039296, 103216337152, 413619611968, 1657501354048, 6642119813120, 26617026736320, 106662654436544

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 5*a(n-2) + 2*a(n-3) - 16*a(n-4) - 28*a(n-5) - 8*a(n-6).

Empirical g.f.: 4*x*(24 + 23*x - 27*x^2 - 147*x^3 - 186*x^4 - 50*x^5) / ((1 - 2*x)*(1 - x - 7*x^2 - 16*x^3 - 16*x^4 - 4*x^5)). - Colin Barker, Nov 08 2018

Example

Some solutions for n=6:
..1....0....0....2....3....3....0....0....3....2....3....1....3....4....0....1
..3....4....1....0....4....4....3....1....1....3....2....4....2....1....3....3
..0....1....3....3....4....3....4....1....0....0....2....2....2....4....0....0
..0....4....4....1....3....0....0....0....3....4....3....2....3....4....2....0
..2....1....3....4....1....4....1....4....0....1....2....0....3....0....3....1
..3....0....0....3....1....0....3....4....2....2....0....0....1....0....0....1
..0....1....2....1....2....0....4....2....2....4....0....4....3....4....2....3
..0....0....0....0....4....4....3....2....3....1....3....4....3....3....3....1

Crossrefs

Column 4 of A248461.

Sequence in context: A292345 A084048 A167983 * A051483 A277107 A292543

Adjacent sequences: A248454 A248455 A248456 * A248458 A248459 A248460

Keyword

nonn

Author

R. H. Hardin, Oct 06 2014

Status

approved