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A200058 Number of -n..n arrays x(0..3) of 4 elements with zero sum and elements alternately strictly increasing and strictly decreasing. 1
4, 26, 78, 172, 324, 546, 850, 1252, 1764, 2398, 3170, 4092, 5176, 6438, 7890, 9544, 11416, 13518, 15862, 18464, 21336, 24490, 27942, 31704, 35788, 40210, 44982, 50116, 55628, 61530, 67834, 74556, 81708, 89302, 97354, 105876, 114880, 124382, 134394 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A200057.

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.: 2*x*(2 + x + x^2)*(1 + 3*x + x^2) / ((1 - x)^4*(1 + x + x^2)). - Colin Barker, May 17 2018

EXAMPLE

Some solutions for n=6:

..2....6...-2....5....6...-2....2...-3....5....2....1....0....3....2....1....6

..5...-6...-3...-2...-4...-3...-4...-4...-5....0....3...-5...-3...-1...-4...-3

.-5....3....5....1....1....3....6....6....6....1...-3....5....1....0....5....0

.-2...-3....0...-4...-3....2...-4....1...-6...-3...-1....0...-1...-1...-2...-3

CROSSREFS

Cf. A200057.

Sequence in context: A099442 A014450 A283573 * A142962 A247194 A102198

Adjacent sequences:  A200055 A200056 A200057 * A200059 A200060 A200061

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 13 2011

STATUS

approved

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Last modified July 23 22:02 EDT 2021. Contains 346265 sequences. (Running on oeis4.)