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 A107848 Number of subsets of the n-th roots of unity summing to a real number. 3
 2, 4, 4, 8, 8, 24, 16, 48, 40, 144, 64, 336, 128, 864, 416, 1728, 512, 8304, 1024, 10656, 4032, 31104, 4096, 116256, 9248, 186624, 40000, 374976, 32768, 3537024, 65536, 2239488 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS T. D. Noe, Sums of Roots of Unity Plots FORMULA For prime n, a(n)=2^((n+1)/2). MATHEMATICA Needs["DiscreteMath`Combinatorica`"]; Table[Plus@@Table[Count[(KSubsets[Range[n], k]), q_List/; Im[Chop[Plus@@(E^(2.*Pi*I*q/n))]]==0], {k, 0, n}], {n, 20}] CROSSREFS Cf. A103314 (number of subsets of the n-th roots of unity summing to zero). Sequence in context: A116596 A248692 A048656 * A285273 A188824 A181212 Adjacent sequences:  A107845 A107846 A107847 * A107849 A107850 A107851 KEYWORD nonn AUTHOR T. D. Noe, May 25 2005 STATUS approved

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Last modified April 20 12:58 EDT 2021. Contains 343135 sequences. (Running on oeis4.)