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A209546 1/4 the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having exactly two distinct clockwise edge differences. 1
7, 20, 61, 191, 603, 1909, 6049, 19173, 60777, 192665, 610761, 1936161, 6137793, 19457329, 61681409, 195535393, 619864097, 1965022785, 6229292161, 19747394881, 62600949633, 198450424449, 629105008769, 1994317286913, 6322158281217 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A209553.

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) - 6*a(n-2) + 2*a(n-4).

Empirical g.f.: x*(7 - 15*x + 3*x^2 + 6*x^3) / ((1 - x)*(1 - 4*x + 2*x^2 + 2*x^3)). - Colin Barker, Jul 11 2018

EXAMPLE

Some solutions for n=4:

..0..1....0..1....3..2....3..0....2..3....0..2....0..1....1..3....1..2....0..1

..3..2....1..2....0..1....0..3....3..2....2..0....3..2....3..1....0..1....1..2

..0..1....2..1....1..2....1..2....2..3....0..2....2..1....1..3....1..2....0..3

..3..2....1..2....0..1....2..3....3..2....2..0....1..2....3..1....2..3....3..0

..2..3....0..1....1..0....1..2....2..3....0..2....2..1....1..3....3..2....2..1

CROSSREFS

Cf. A209553.

Sequence in context: A055267 A218843 A219422 * A222549 A196584 A301777

Adjacent sequences:  A209543 A209544 A209545 * A209547 A209548 A209549

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 10 2012

STATUS

approved

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Last modified April 7 01:11 EDT 2020. Contains 333291 sequences. (Running on oeis4.)