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A239024
Number of n X 2 0..2 arrays with no element equal to the sum of elements to its left or one plus the sum of elements above it, modulo 3.
1
1, 3, 4, 11, 16, 43, 64, 171, 256, 683, 1024, 2731, 4096, 10923, 16384, 43691, 65536, 174763, 262144, 699051, 1048576, 2796203, 4194304, 11184811, 16777216, 44739243, 67108864, 178956971, 268435456, 715827883, 1073741824, 2863311531, 4294967296
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 5*a(n-2) - 4*a(n-4).
Conjectures from Colin Barker, Oct 25 2018: (Start)
G.f.: x*(1 + 3*x - x^2 - 4*x^3) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 + 2*x)).
a(n) = (2 + (-2)^n + 2*(-1)^n + 7*2^n) / 12.
(End)
EXAMPLE
Some solutions for n=5:
..2..0....2..0....2..0....2..0....2..0....2..0....2..0....2..0....2..0....2..0
..1..0....2..0....2..0....2..0....1..2....1..0....1..0....2..0....2..0....1..0
..2..0....1..2....1..0....1..2....2..1....2..0....2..0....1..2....1..2....2..0
..2..0....2..1....1..0....1..2....1..0....1..0....1..2....2..1....1..2....2..0
..1..2....1..2....2..0....2..1....2..0....2..0....2..1....1..0....2..0....1..0
CROSSREFS
Column 2 of A239030.
Sequence in context: A007382 A127804 A027306 * A026676 A142870 A324552
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 09 2014
STATUS
approved