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A185561
1/4 the number of n X 3 0..3 arrays with no element equal both to the element above and to the element to its left.
1
16, 900, 50580, 2842560, 159749820, 8977824540, 504547256880, 28355191537860, 1593541291098420, 89555869973406240, 5032975230384726780, 282849573983126145660, 15895941831670877597520, 893340453575999346503940
OFFSET
1,1
COMMENTS
Column 3 of A185567.
LINKS
FORMULA
Empirical: a(n) = 57*a(n-1) - 45*a(n-2).
Empirical g.f.: 4*x*(4 - 3*x) / (1 - 57*x + 45*x^2). - Colin Barker, Apr 16 2018
EXAMPLE
Some solutions for 5 X 3 with a(1,1)=0:
..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
..0..2..2....0..2..0....0..2..0....0..2..2....0..2..0....0..2..0....0..2..0
..2..0..1....0..1..3....0..2..1....0..3..2....0..1..0....0..3..2....0..2..3
..0..1..3....2..2..2....1..2..2....3..0..3....3..2..3....0..3..3....0..2..3
..3..3..0....1..2..0....3..3..3....0..3..1....0..1..0....3..1..0....1..1..3
CROSSREFS
Cf. A185567.
Sequence in context: A272468 A214386 A367089 * A369583 A283946 A289707
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 31 2011
STATUS
approved