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A212824 Number of 0..3 arrays of length n with no adjacent pair equal to its immediately preceding adjacent pair, and new values introduced in 0..3 order. 1
1, 2, 5, 13, 43, 152, 559, 2091, 7882, 29809, 112895, 427824, 1621691, 6147791, 23307226, 88363077, 335007715, 1270107208, 4815336407, 18256317315, 69214939274, 262413734345, 994885963543, 3771899000928, 14300354743363 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A212829.

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) + a(n-2) - 6*a(n-3) - 3*a(n-4) for n>7.

Empirical g.f.: x*(1 + x + x^2)*(1 - 3*x - 2*x^2 + 2*x^3 + x^4) / ((1 - x - x^2)*(1 - 3*x - 3*x^2)). - Colin Barker, Jul 21 2018

EXAMPLE

Some solutions for n=8:

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

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

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

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

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

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

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

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

CROSSREFS

Cf. A212829.

Sequence in context: A299430 A307263 A278171 * A286949 A287023 A287008

Adjacent sequences:  A212821 A212822 A212823 * A212825 A212826 A212827

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 28 2012

STATUS

approved

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Last modified November 11 22:31 EST 2019. Contains 329046 sequences. (Running on oeis4.)