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A233099
Number of 2 X n 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, diagonally or antidiagonally, top left element zero, and 1 appearing before 2 in row major order.
1
3, 11, 65, 386, 2315, 13886, 83315, 499886, 2999315, 17995886, 107975315, 647851886, 3887111315, 23322667886, 139936007315, 839616043886, 5037696263315, 30226177579886, 181357065479315, 1088142392875886
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) + a(n-2) - 6*a(n-3) for n>4.
Conjectures from Colin Barker, Oct 07 2018: (Start)
G.f.: x*(3 - 7*x - 4*x^2 + 3*x^3) / ((1 - x)*(1 + x)*(1 - 6*x)).
a(n) = (24 + 25*6^n) / 84 for n even.
a(n) = (60 + 25*6^n) / 84 for n>1 and odd.
(End)
EXAMPLE
Some solutions for n=5:
..0..1..0..1..3....0..1..3..2..0....0..0..0..0..1....0..1..1..1..0
..0..0..1..1..3....0..2..0..1..0....1..0..1..0..1....0..0..1..0..1
CROSSREFS
Row 2 of A233098.
Sequence in context: A096655 A030226 A309174 * A372395 A132101 A280775
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 04 2013
STATUS
approved