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A188250 Number of arrangements of 4 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero 1
0, 20, 52, 144, 208, 436, 532, 816, 1072, 1508, 1668, 2400, 2592, 3220, 3940, 4768, 5024, 6212, 6500, 7856, 8944, 9988, 10340, 12384, 13280, 14516, 15796, 17824, 18272, 21156, 21636, 23712, 25472, 27124, 29124, 32800, 33376, 35220, 37300, 41136, 41776 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 2 of A188249

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..135

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A183047 A209982 A205220 * A008524 A302885 A059677

Adjacent sequences:  A188247 A188248 A188249 * A188251 A188252 A188253

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 25 2011

STATUS

approved

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Last modified September 16 12:28 EDT 2019. Contains 327098 sequences. (Running on oeis4.)