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A200431 Number of -n..n arrays x(0..3) of 4 elements with zero sum and no two or three adjacent elements summing to zero. 1
0, 20, 92, 248, 520, 940, 1540, 2352, 3408, 4740, 6380, 8360, 10712, 13468, 16660, 20320, 24480, 29172, 34428, 40280, 46760, 53900, 61732, 70288, 79600, 89700, 100620, 112392, 125048, 138620, 153140, 168640, 185152, 202708, 221340, 241080 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 1 of A200430.

LINKS

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

FORMULA

Empirical: a(n) = (16/3)*n^3 - 6*n^2 + (2/3)*n.

Conjectures from Colin Barker, May 20 2018: (Start)

G.f.: 4*x^2*(5 + 3*x) / (1 - x)^4.

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.

(End)

EXAMPLE

Some solutions for n=3:

.-3...-2....1....3...-3....2...-3...-1....2....1...-1...-1....1....3...-2...-1

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

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

..2...-1...-2...-1...-1...-3....2...-2....2...-3...-1....3....1....2....3...-1

CROSSREFS

Cf. A200430.

Sequence in context: A281768 A225892 A211140 * A172200 A177291 A169711

Adjacent sequences:  A200428 A200429 A200430 * A200432 A200433 A200434

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 17 2011

STATUS

approved

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Last modified August 4 16:25 EDT 2021. Contains 346447 sequences. (Running on oeis4.)