

A212823


Number of 0..2 arrays of length n with no adjacent pair equal to its immediately preceding adjacent pair, and new values introduced in 0..2 order.


1



1, 2, 5, 12, 33, 90, 246, 672, 1836, 5016, 13704, 37440, 102288, 279456, 763488, 2085888, 5698752, 15569280, 42536064, 116210688, 317493504, 867408384, 2369803776, 6474424320, 17688456192, 48325761024, 132028434432, 360708390912
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OFFSET

1,2


COMMENTS

Column 2 of A212829.


LINKS

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


FORMULA

Empirical: a(n) = 2*a(n1) + 2*a(n2) for n>5.
Empirical g.f.: x*(1  x  x^2)*(1 + x + x^2) / (1  2*x  2*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
..1....1....1....1....1....1....0....1....1....1....0....1....1....1....1....1
..2....2....1....2....2....2....0....0....2....1....1....1....0....0....2....2
..1....0....0....2....2....0....1....2....0....1....2....2....2....0....0....0
..0....0....2....2....0....1....2....1....0....2....2....0....1....1....2....2
..0....1....0....0....1....1....2....0....0....0....0....0....0....2....2....2
..1....0....0....2....0....0....1....0....1....0....0....1....2....2....0....2
..1....0....1....2....0....2....2....0....1....0....2....0....1....0....1....0


CROSSREFS

Cf. A212829.
Sequence in context: A209717 A000560 A292212 * A292213 A032124 A292214
Adjacent sequences: A212820 A212821 A212822 * A212824 A212825 A212826


KEYWORD

nonn


AUTHOR

R. H. Hardin, May 28 2012


STATUS

approved



