OFFSET
0,5
COMMENTS
A reflex angle is an angle with measure greater than Pi or 180 degrees. Every polygon has at least three angles with measure less than Pi or 180 degrees.
LINKS
Danny Rorabaugh, Table of n, a(n) for n = 0..500
Danny Rorabaugh, Polygon demonstration of a(6)=9
FORMULA
a(n) = A000031(n) - 2 - floor(n/2), n>0.
EXAMPLE
Let 1's represent black beads and 0's represent white beads. For n=6, the a(6)=9 necklaces are 000000, 000001, 000011, 000101, 000111, 001001, 001011, 001101, 010101. Note that 001011 and 001101 would be equivalent if "turning over" were allowed.
PROG
(Sage) [sum([Necklaces([n-k, k]).cardinality() for k in range(n-2)]) for n in range(34)]
CROSSREFS
KEYWORD
nonn
AUTHOR
Danny Rorabaugh, Sep 15 2015
STATUS
approved