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 A164896 Number of subsets (up to cyclic shifts) of the n-th roots of 1 with zero sum. 2
 1, 2, 2, 3, 2, 5, 2, 6, 4, 9, 2, 19, 2, 21, 10, 36, 2, 94, 2, 117, 22, 189, 2, 618, 8, 633, 60, 1203, 2, 6069, 2, 4116, 190, 7713, 26, 35324, 2, 27597, 634, 59706, 2, 328835, 2, 190935, 2728, 364725, 2, 2435780, 20, 1579884, 7714, 2582061, 2, 21013770, 194, 9894294, 27598, 18512793, 2, 377367015, 2, 69273669, 104832, 134219796, 638, 1678410951 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Cyclic shifts correspond to multiplication by a root of unity. a(n)=2 for n prime, corresponding to the empty and the full subset. [Joerg Arndt, Jun 10 2011] LINKS Joerg Arndt, Matters Computational (The Fxtbook), section 18.4 "Sums of roots of unity that are zero", p.383 FORMULA a(n) = A110981(n) + sum_{d|n,d

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Last modified April 11 18:59 EDT 2021. Contains 342888 sequences. (Running on oeis4.)