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A230920
Number of n X 2 0..2 arrays x(i,j) with each element horizontally, vertically, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 3 and at least one element with value (x(i,j)-1) mod 3, and upper left element zero.
1
0, 12, 54, 432, 3108, 22428, 162504, 1175592, 8507376, 61562808, 445491480, 3223753560, 23328341064, 168813022728, 1221597213768, 8839956302856, 63969389202792, 462907576993032, 3349780692313320, 24240326242963080
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 5*a(n-1) + 14*a(n-2) + 16*a(n-3) - 2*a(n-4) + 4*a(n-5).
Empirical g.f.: 6*x^2*(1 - x)*(2 + x) / (1 - 5*x - 14*x^2 - 16*x^3 + 2*x^4 - 4*x^5). - Colin Barker, Sep 23 2018
EXAMPLE
Some solutions for n=3:
..0..1....0..0....0..2....0..1....0..0....0..0....0..1....0..1....0..2....0..1
..1..2....2..1....1..2....1..2....1..2....1..2....2..2....2..0....1..0....2..1
..0..1....0..1....0..1....0..2....0..0....0..1....1..0....0..1....0..2....0..2
CROSSREFS
Column 2 of A230926.
Sequence in context: A126399 A137938 A009726 * A190948 A275249 A143856
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 01 2013
STATUS
approved