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A251336
Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock summing to a nonzero multiple of 3.
1
85, 455, 2450, 13275, 72375, 397000, 2190625, 12156875, 67831250, 380409375, 2143546875, 12131500000, 68933828125, 393119609375, 2249232031250, 12906582421875, 74253193359375, 428169484375000, 2473966416015625
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 10*a(n-1) - 20*a(n-2) - 25*a(n-3).
Empirical g.f.: 5*x*(17 - 79*x - 80*x^2) / ((1 - 5*x)*(1 - 5*x - 5*x^2)). - Colin Barker, Nov 29 2018
EXAMPLE
Some solutions for n=4:
..1..2....0..2....0..2....3..2....3..1....1..0....1..2....0..2....0..0....2..1
..0..3....0..1....3..1....1..0....2..0....2..0....2..1....1..0....3..3....0..3
..3..0....2..0....0..2....2..3....2..2....2..2....1..2....0..2....1..2....0..3
..0..0....1..3....0..1....3..1....0..2....3..2....2..1....2..2....3..0....0..0
..2..1....2..3....3..2....2..0....3..1....3..1....0..3....3..2....3..0....2..1
CROSSREFS
Column 1 of A251343.
Sequence in context: A297399 A020212 A251343 * A262425 A264425 A250463
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 01 2014
STATUS
approved