A243601 - OEIS

A243601

Number of length n+2 0..4 arrays with no three elements in a row with pattern aba (with a!=b) and new values 0..4 introduced in 0..4 order.

4, 10, 29, 96, 349, 1350, 5425, 22297, 92841, 389456, 1640630, 6927937, 29294645, 123967625, 524830618, 2222483751, 9412820990, 39869076285, 168877805414, 715352976032, 3030223762722, 12836088840031, 54374194848619

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OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 8*a(n-1) - 18*a(n-2) + 5*a(n-3) + 17*a(n-4) - 4*a(n-5) - 6*a(n-6) - a(n-7).

Empirical g.f.: x*(4 - 22*x + 21*x^2 + 24*x^3 - 15*x^4 - 13*x^5 - 2*x^6) / ((1 - x)*(1 - x - x^2)*(1 - 2*x - x^2)*(1 - 4*x - x^2)). - Colin Barker, Nov 02 2018

EXAMPLE

Some solutions for n=5:

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

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

..1....2....1....2....2....1....1....2....1....2....2....2....2....2....2....2

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

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

..3....2....2....0....2....1....0....3....3....1....4....4....0....3....1....3

..1....3....2....2....4....3....2....3....4....1....2....4....2....4....3....2

CROSSREFS

Column 4 of A243607.

Sequence in context: A233347 A264158 A152808 * A243602 A243603 A243604

Adjacent sequences: A243598 A243599 A243600 * A243602 A243603 A243604

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 07 2014

STATUS

approved