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A243635 Number of length n+2 0..4 arrays with no three unequal elements in a row and new values 0..4 introduced in 0..4 order. 1
4, 9, 21, 51, 127, 324, 844, 2242, 6062, 16655, 46411, 130937, 373349, 1074194, 3114146, 9085176, 26643492, 78470989, 231925649, 687430207, 2042284587, 6078844480, 18121207896, 54086361422, 161592030394, 483170313579 (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) = 7*a(n-1) - 14*a(n-2) + 21*a(n-4) - 7*a(n-5) - 6*a(n-6).

Empirical g.f.: x*(4 - 19*x + 14*x^2 + 30*x^3 - 20*x^4 - 12*x^5) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - 3*x)*(1 - 2*x - x^2)). - Colin Barker, Nov 02 2018

EXAMPLE

Some solutions for n=6:

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

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

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

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

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

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

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

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

CROSSREFS

Column 4 of A243641.

Sequence in context: A297296 A048582 A069231 * A243636 A243637 A243638

Adjacent sequences:  A243632 A243633 A243634 * A243636 A243637 A243638

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 08 2014

STATUS

approved

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Last modified March 25 03:50 EDT 2019. Contains 321450 sequences. (Running on oeis4.)