|
|
A175955
|
|
Number of ways to connect with nonintersecting chords n unlabeled points equally spaced on a circle such that the resulting configuration is not invariant w.r.t. rotation any angle < 2*Pi.
|
|
1
|
|
|
1, 0, 1, 1, 4, 6, 18, 36, 92, 209, 527, 1269, 3218, 8063, 20701, 53209, 138634, 362789, 957857, 2541735, 6787960, 18214250, 49120018, 133024306, 361736098, 987284765, 2703991469, 7429359867, 20473889132, 56579399002, 156766505690
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,5
|
|
COMMENTS
|
Also, number of chord configurations on n vertices of the period n.
Number of such chord configurations on 2n vertices with n chords is given by A005354(n+1).
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
For n=2, there are only two configurations possible: two diametrically located points on a circle connected or not connected with a chord. Since both these configurations are invariant w.r.t. rotation by angle Pi, a(2)=0.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|