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A268093 Number of 1 X n 0..2 arrays with every repeated value in every row not one larger and in every column one larger mod 3 than the previous repeated value, and upper left element zero. 1
1, 3, 9, 26, 74, 208, 580, 1608, 4440, 12224, 33584, 92128, 252448, 691200, 1891392, 5173376, 14145920, 38671360, 105700096, 288873984, 789410304, 2157092864, 5894054912, 16104392704, 44001089536, 120219353088, 328457662464 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 4*a(n-3).
Conjectures from Colin Barker, Jan 11 2019: (Start)
G.f.: x*(1 - x - x^2) / ((1 - 2*x)*(1 - 2*x - 2*x^2)).
a(n) = (-3*2^n + (3-2*sqrt(3))*(1-sqrt(3))^n + (1+sqrt(3))^n*(3+2*sqrt(3))) / 12.
(End)
EXAMPLE
Some solutions for n=4:
..0..2..2..1....0..2..1..0....0..0..1..2....0..0..2..2....0..0..2..0
CROSSREFS
Row 1 of A268092.
Sequence in context: A061667 A234270 A258911 * A127911 A116423 A077845
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 26 2016
STATUS
approved

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Last modified June 16 19:52 EDT 2024. Contains 373432 sequences. (Running on oeis4.)