// output of ./demo/comb/root-sums-demo.cc:
// Description:
//% Zero-sums of roots of unity.
//% Cf. OEIS sequence A164896.

arg 1: 12 == n  [n-th roots of unity]  default=12
   1:  ............   1   
   2:  .....1.....1   6    0 6
   3:  ....11....11   6    0 1 6 7
   4:  ...1...1...1   4    0 4 8
   5:  ...1.1...1.1   6    0 2 6 8
   6:  ...11..1..11  12 L  0 1 4 7 8
   7:  ...111...111   6    0 1 2 6 7 8
   8:  ..1..1..1..1   3    0 3 6 9
   9:  ..1.11..1.11   6    0 1 3 6 7 9
  10:  ..11..11..11   4    0 1 4 5 8 9
  11:  ..11.1..11.1   6    0 2 3 6 8 9
  12:  ..11.11..111  12 L  0 1 2 5 6 8 9
  13:  ..1111..1111   6    0 1 2 3 6 7 8 9
  14:  .1.1.1.1.1.1   2    0 2 4 6 8 10
  15:  .1.111.1.111   6    0 1 2 4 6 7 8 10
  16:  .11.11.11.11   3    0 1 3 4 6 7 9 10
  17:  .111.111.111   4    0 1 2 4 5 6 8 9 10
  18:  .11111.11111   6    0 1 2 3 4 6 7 8 9 10
  19:  111111111111   1    0 1 2 3 4 5 6 7 8 9 10 11

  ct=19  act=2  sj=100
