A108417 Number of subsets of the n-th roots of 1 with absolute value of sum = 1.

0, 1, 2, 6, 8, 10, 36, 14, 64, 72, 180, 22, 720, 26, 924, 600, 2048, 34, 10800, 38, 12240, 2856, 22572, 46, 144000

Offset

0,3

Comments

a(n) is divisible by n (rotation symmetry). a(n)/n differs from A107754 by a factor of 2 for odd n.

Links

Table of n, a(n) for n=0..24.

Mathematica

<<DiscreteMath`Combinatorica`; Table[Plus @@ Count[KSubsets[Range[n], k], q_List/; Chop[ -1+Abs[Plus @@ (E^((2.*Pi*I*q)/n))]] === 0], {n, 16}, {k, 0, n}]

Crossrefs

Row sums of A108416.

Cf. A107754, A103314.

Sequence in context: A362667 A299381 A247984 * A373057 A185078 A214402

Adjacent sequences: A108414 A108415 A108416 * A108418 A108419 A108420

Keyword

nonn,more

Author

Wouter Meeussen, Jun 02 2005

Status

approved