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 A125873 Prime numbers n such that cos(2pi/n) is an algebraic number of an 11-smooth degree, but not 7-smooth. 0
 23, 67, 89, 199, 331, 353, 397, 463, 617, 661, 727, 881, 991, 1321, 1409, 1453, 1783, 2113, 2179, 2311, 2377, 2663, 2971, 3169, 3301, 3389, 3631, 3697, 3851, 4159, 4357, 4621, 4951, 5281, 5347, 5501, 6337, 6469, 7129, 7393, 7547, 8317, 8713 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..43. MATHEMATICA Do[If[Take[FactorInteger[EulerPhi[2n+1]][[ -1]], 1]=={11} && PrimeQ[2n+1], Print[2n+1]], {n, 1, 10000}] (*Artur Jasinski*) CROSSREFS Cf. A125866-A125878. Sequence in context: A228611 A104945 A141849 * A059241 A241212 A052087 Adjacent sequences: A125870 A125871 A125872 * A125874 A125875 A125876 KEYWORD nonn AUTHOR Artur Jasinski, Dec 13 2006 EXTENSIONS Edited by Don Reble, Apr 24 2007 STATUS approved

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Last modified October 1 14:44 EDT 2023. Contains 365826 sequences. (Running on oeis4.)