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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.
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2014
STATUS
approved