A248428 Number of length n+2 0..3 arrays with every three consecutive terms having the sum of some two elements equal to twice the third.

16, 20, 24, 28, 36, 44, 52, 68, 84, 100, 132, 164, 196, 260, 324, 388, 516, 644, 772, 1028, 1284, 1540, 2052, 2564, 3076, 4100, 5124, 6148, 8196, 10244, 12292, 16388, 20484, 24580, 32772, 40964, 49156, 65540, 81924, 98308, 131076, 163844, 196612, 262148

Offset

1,1

Links

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

Formula

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

Empirical g.f.: 4*x*(4 + x + x^2 - 7*x^3) / ((1 - x)*(1 - 2*x^3)). - Colin Barker, Nov 08 2018

Example

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

Crossrefs

Column 3 of A248433.

Sequence in context: A044860 A272533 A161424 * A088449 A104010 A102544

Adjacent sequences: A248425 A248426 A248427 * A248429 A248430 A248431

Keyword

nonn

Author

R. H. Hardin, Oct 06 2014

Status

approved