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A243038 Number of length n+3 0..2 arrays with no four elements in a row with pattern abab (with a!=b) and new values 0..2 introduced in 0..2 order. 1
13, 36, 101, 285, 806, 2281, 6457, 18280, 51753, 146521, 414826, 1174445, 3325061, 9413836, 26652237, 75457205, 213632718, 604832081, 1712386801, 4848070480, 13725746641, 38860021041, 110019605842, 311485000405, 881869233533 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) - a(n-3) - a(n-4).

Empirical g.f.: x*(13 - 3*x - 7*x^2 - 5*x^3) / ((1 - x)*(1 - 2*x - 2*x^2 - x^3)). - Colin Barker, Nov 01 2018

EXAMPLE

Some solutions for n=4:

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

..1....1....0....0....0....1....1....1....0....1....1....0....1....1....0....1

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

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

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

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

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

CROSSREFS

Column 2 of A243044.

Sequence in context: A051865 A081928 A034129 * A297303 A225131 A118361

Adjacent sequences:  A243035 A243036 A243037 * A243039 A243040 A243041

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 29 2014

STATUS

approved

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Last modified December 14 17:32 EST 2019. Contains 329979 sequences. (Running on oeis4.)