

A108417


Number of subsets of the nth roots of 1 with absolute value of sum = 1.


2



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
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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: A066198 A299381 A247984 * A185078 A214402 A166064
Adjacent sequences: A108414 A108415 A108416 * A108418 A108419 A108420


KEYWORD

nonn,more


AUTHOR

Wouter Meeussen, Jun 02 2005


STATUS

approved



