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A199706 Number of -n..n arrays x(0..3) of 4 elements with zero sum and no two neighbors equal. 1
8, 52, 168, 380, 724, 1236, 1940, 2872, 4068, 5552, 7360, 9528, 12080, 15052, 18480, 22388, 26812, 31788, 37340, 43504, 50316, 57800, 65992, 74928, 84632, 95140, 106488, 118700, 131812, 145860, 160868, 176872, 193908, 212000, 231184, 251496 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A199704.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

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

Empirical g.f.: 4*x*(2 + 7*x + 9*x^2 + 4*x^3 + 2*x^4) / ((1 - x)^4*(1 + x + x^2)). - Colin Barker, May 16 2018

EXAMPLE

Some solutions for n=5:

..3...-3....3....2....2....2....2...-5...-2...-3....2....0....4...-3....4...-5

..0...-5...-3...-4....1...-1...-1....5...-4....3....0...-2...-4...-2...-3....3

.-3....3...-4...-2...-5....4....0....3....1....5....2...-3...-1....1...-4....4

..0....5....4....4....2...-5...-1...-3....5...-5...-4....5....1....4....3...-2

CROSSREFS

Cf. A199704.

Sequence in context: A238648 A215834 A180319 * A302318 A035288 A303012

Adjacent sequences:  A199703 A199704 A199705 * A199707 A199708 A199709

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 09 2011

STATUS

approved

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Last modified October 19 13:01 EDT 2019. Contains 328222 sequences. (Running on oeis4.)