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A107753 Number of primitive subsets of the n-th roots of unity summing to zero. 3
1, 2, 2, 3, 2, 6, 2, 5, 4, 8, 2, 11, 2, 10, 9, 9, 2, 16, 2, 15, 11, 14, 2, 21, 6, 16, 10, 19, 2, 212, 2, 17, 15, 20, 13, 31, 2, 22, 17, 29, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A primitive subset has no nonempty proper subset whose members sum to zero. Note that a(30) is the first term for which the formulas do not apply. For n=30, there are 1,0,15,10,0,5,30,60,60,30 primitive subsets of size 0,1,2,...,9.

LINKS

Table of n, a(n) for n=1..41.

FORMULA

For primes p and q, if n = p^i, then a(n)=1+n/p; if n=p^i q^j, then a(n)=1+n/p+n/q.

CROSSREFS

Cf. A103314 (number of subsets of the n-th roots of unity summing to zero), A107754 (number of subsets of the n-th roots of unity summing to one).

Sequence in context: A329607 A108499 A260895 * A197929 A326849 A328706

Adjacent sequences:  A107750 A107751 A107752 * A107754 A107755 A107756

KEYWORD

nonn

AUTHOR

T. D. Noe, May 23 2005

STATUS

approved

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Last modified July 6 23:56 EDT 2020. Contains 335484 sequences. (Running on oeis4.)