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A188351 Number of arrangements of n+1 numbers x(i) in -2..2 with the sum of x(i)*x(i+1) equal to zero 1
9, 45, 117, 565, 1953, 9153, 37269, 173409, 766869, 3589357, 16545861, 78195505, 368573829, 1757922765, 8394885777, 40340645213, 194259462205, 938930726781, 4547344031581, 22077243778089, 107366485176765, 523060579628697 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A188358

LINKS

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

EXAMPLE

Some solutions for n=4

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

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

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

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

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

CROSSREFS

Sequence in context: A321779 A068314 A152996 * A220443 A289721 A060008

Adjacent sequences:  A188348 A188349 A188350 * A188352 A188353 A188354

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 28 2011

STATUS

approved

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Last modified July 28 17:15 EDT 2021. Contains 346335 sequences. (Running on oeis4.)