There are 2^n sums of the n-th roots of unity.
Table of n, a(n) for n=1..20.
T. D. Noe, Sums of Roots of Unity Plots
a(4)=2 because the nonzero sums of 4th roots of unity have magnitude 1 or sqrt(2).
Cf. A103314 (number of subsets of the n-th roots of unity summing to zero).
Sequence in context: A011155 A161136 A258163 * A238761 A261469 A292498
Adjacent sequences: A108378 A108379 A108380 * A108382 A108383 A108384
T. D. Noe, Jun 01 2005