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A209505

Half the number of (n+1) X 3 0..2 arrays with every 2 X 2 subblock having two or four distinct clockwise edge differences.

27, 123, 561, 2559, 11673, 53247, 242889, 1107951, 5053977, 23053983, 105161961, 479701839, 2188185273, 9981522687, 45531242889, 207693169071, 947403359577, 4321630459743, 19713345579561, 89923466978319, 410190643732473

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Column 2 of A209511.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 5*a(n-1) -2*a(n-2).

Empirical g.f.: 3*x*(9 - 4*x) / (1 - 5*x + 2*x^2). - Colin Barker, Jul 10 2018

EXAMPLE

Some solutions for n=4:

..2..0..1....2..1..2....2..0..1....2..0..1....2..1..0....0..2..1....1..2..1

..0..1..0....0..2..1....0..2..0....0..1..2....0..2..1....1..0..2....0..1..2

..2..0..1....1..0..2....1..0..1....2..0..1....1..0..2....2..1..0....1..2..1

..0..1..2....0..1..0....2..1..0....1..2..0....2..1..0....1..2..1....0..1..2

..1..2..0....2..0..1....1..0..2....2..1..2....0..2..1....2..0..2....1..0..1

CROSSREFS

Cf. A209511.

Sequence in context: A087795 A036927 A232025 * A275430 A381951 A145555

Adjacent sequences: A209502 A209503 A209504 * A209506 A209507 A209508

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 09 2012

STATUS

approved

URL: https://oeis.org/A209505

⇱ A209505 - OEIS