OFFSET
1,1
LINKS
FORMULA
For prime n, a(n)=2^((n+1)/2).
MATHEMATICA
Needs["DiscreteMath`Combinatorica`"]; Table[Plus@@Table[Count[(KSubsets[Range[n], k]), q_List/; Im[Chop[Plus@@(E^(2.*Pi*I*q/n))]]==0], {k, 0, n}], {n, 20}]
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, May 25 2005
STATUS
approved