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A108380 Least number of distinct n-th roots of unity summing to the smallest possible nonzero magnitude. 3
1, 1, 1, 1, 2, 1, 2, 3, 2, 3, 5, 5, 6, 6, 4, 5, 5, 5, 7, 7, 10, 5, 8, 7, 12, 7, 10, 9, 14, 13, 11, 7, 14, 11, 17, 9, 18, 14, 18, 9, 19, 12, 17, 15, 14, 14, 22, 15, 16, 20, 20, 17, 18, 22, 23, 17, 24, 19, 26, 21, 29, 18, 26, 19, 26, 31, 30, 27, 31, 17, 32, 23, 34 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Myerson writes about the unsolved problem of finding a good lower bound on the least magnitude as a function of n. Note that a(n)<n/2 for n>2 because the sum of all n-th roots of unity is 0.

LINKS

Table of n, a(n) for n=1..73.

Gerald Myerson, How small can a sum of roots of unity be?, Amer. Math. Monthly, Vol. 93 (1986), No. 6, 457-459.

T. D. Noe, Plot of the least magnitude for n<=81

EXAMPLE

a(8)=3 because the least nonzero magnitude is sqrt(2)-1, which is the sum of three 8th roots of unity.

CROSSREFS

Cf. A103314 (number of subsets of the n-th roots of unity summing to zero).

Sequence in context: A029167 A161103 A147301 * A302098 A112779 A029201

Adjacent sequences:  A108377 A108378 A108379 * A108381 A108382 A108383

KEYWORD

nonn

AUTHOR

T. D. Noe, Jun 01 2005, extended Jun 04 2005

STATUS

approved

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Last modified July 19 12:35 EDT 2019. Contains 325159 sequences. (Running on oeis4.)