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A209497
Number of n X 2 0..4 arrays with every 2 X 2 subblock containing exactly one value repeat, and new values 0..4 introduced in row major order.
1
2, 6, 57, 690, 9393, 133380, 1920126, 27760512, 401882796, 5820335088, 84304518360, 1221153876288, 17688664980912, 256224877720896, 3711487617186912, 53761934301895680, 778756709322725568
OFFSET
1,1
COMMENTS
Column 2 of A209503.
LINKS
FORMULA
Empirical: a(n) = 16*a(n-1) - 10*a(n-2) - 168*a(n-3) - 72*a(n-4) for n>5.
Empirical g.f.: x*(2 - 26*x - 19*x^2 + 174*x^3 + 75*x^4) / ((1 - 4*x - 2*x^2)*(1 - 12*x - 36*x^2)). - Colin Barker, Jul 10 2018
EXAMPLE
Some solutions for n=4.
..0..0....0..0....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..0
..1..2....1..2....0..2....1..2....1..2....1..2....1..2....1..2....1..2....1..2
..3..1....2..0....1..0....0..1....2..3....0..2....1..0....0..1....0..2....2..3
..2..1....0..3....2..0....0..2....2..1....3..2....2..0....2..1....1..0....4..2
CROSSREFS
Cf. A209503.
Sequence in context: A198445 A248377 A326968 * A209738 A209459 A209521
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 09 2012
STATUS
approved