login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A188242 Number of arrangements of n+2 nonzero numbers x(i) in -2..2 with the sum of x(i)*x(i+1) equal to zero 1
16, 20, 120, 300, 1284, 4132, 16272, 57808, 223308, 828456, 3193588, 12106616, 46777036, 179484068, 695670728, 2689241588, 10454975104, 40616587968, 158328346172, 617266507080, 2411727117520, 9427476168776, 36906793159556 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A188249

LINKS

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

EXAMPLE

Some solutions for n=4

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

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

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

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

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

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

CROSSREFS

Sequence in context: A219395 A260572 A240038 * A103330 A045667 A045658

Adjacent sequences:  A188239 A188240 A188241 * A188243 A188244 A188245

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 25 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 30 02:32 EDT 2020. Contains 338076 sequences. (Running on oeis4.)