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Search: id:A108417
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| A108417 |
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Counts the subsets of the n-th roots of 1 with absolute value of sum =1. |
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+0
3
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| 0, 1, 2, 6, 8, 10, 36, 14, 64, 72, 180, 22, 720, 26, 924, 600, 2048, 34, 10800, 38, 12240, 2856, 22572, 46, 144000
(list; table; graph; listen)
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OFFSET
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0,3
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COMMENT
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a(n) is divisible by n (rotation symmetry). Row sums of A108416; a(n)/n differs from A107754 by a factor of 2 for odd n.
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MATHEMATICA
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<<DiscreteMath`Combinatorica`; Table[Plus @@ Count[KSubsets[Range[n], k], q_List/; Chop[ -1+Abs[Plus @@ (E^((2.*Pi*I*q)/n))]] === 0], {n, 16}, {k, 0, n}]
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CROSSREFS
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Cf. A107754, A103314, A108416.
Sequence in context: A118257 A066762 A066198 this_sequence A088417 A050880 A120764
Adjacent sequences: A108414 A108415 A108416 this_sequence A108418 A108419 A108420
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KEYWORD
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nonn,tabl
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AUTHOR
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Wouter Meeussen (wouter.meeussen(AT)pandora.be), Jun 02 2005
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