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A188253 Number of arrangements of 7 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero 0
40, 1284, 12692, 58824, 193232, 521124, 1142180, 2347608, 4323448, 7567844, 12129300, 19691552, 29057776, 42900188, 61593740, 86648240 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 5 of A188249

LINKS

Table of n, a(n) for n=1..16.

EXAMPLE

Some solutions for n=4

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

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

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

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

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

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

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

CROSSREFS

Sequence in context: A278381 A251202 A239189 * A049396 A135644 A165371

Adjacent sequences:  A188250 A188251 A188252 * A188254 A188255 A188256

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 25 2011

STATUS

approved

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Last modified October 15 07:56 EDT 2019. Contains 328026 sequences. (Running on oeis4.)