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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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 28 2011
STATUS
approved

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Last modified December 6 20:19 EST 2023. Contains 367614 sequences. (Running on oeis4.)