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A107754 Number of subsets of the n-th roots of unity that sum to 1. 7
1, 1, 1, 2, 1, 6, 1, 8, 4, 18, 1, 60, 1, 66, 20, 128, 1, 600, 1, 612, 68, 1026, 1, 6000, 16, 4098, 256, 8580, 1, 95226, 1, 32768 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..32.

FORMULA

For prime p, a(p^i) = 2^(p^(i-1)-1).

MATHEMATICA

<< DiscreteMath`Combinatorica`; f[n_] := Plus @@ Table[ Count[ KSubsets[ Range[n], k], q_List /; Chop[ -1 + Plus @@ (E^((2.*Pi*I*q)/n))] === 0], {k, 0, n}]; Table[ f[n], {n, 24}] (* Robert G. Wilson v, Jun 03 2005 *)

CROSSREFS

Cf. A103314 (number of subsets of the n-th roots of unity summing to zero) and A108417 (number of subsets of the n-th roots of unity summing to the absolute value of 1).

Sequence in context: A324193 A264859 A007956 * A181569 A274085 A302129

Adjacent sequences: A107751 A107752 A107753 * A107755 A107756 A107757

KEYWORD

nonn,more

AUTHOR

T. D. Noe, May 23 2005

STATUS

approved

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Last modified January 27 08:50 EST 2023. Contains 359838 sequences. (Running on oeis4.)