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 A125876 Prime numbers n such that cos(2pi/n) is an algebraic number of a 13-smooth degree, but not 11-smooth. 0
 53, 79, 131, 157, 313, 521, 547, 677, 859, 911, 937, 1093, 1171, 1249, 1301, 1873, 1951, 2003, 2029, 2081, 2341, 2549, 2731, 2861, 3121, 3251, 3329, 3433, 3511, 3719, 3823, 4057, 4733, 4993, 5851, 6007, 6553, 6761, 7151, 7489, 7723, 8009 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS MATHEMATICA Do[If[Take[FactorInteger[EulerPhi[2n+1]][[ -1]], 1]=={13} && PrimeQ[2n+1], Print[2n+1]], {n, 1, 10000}] (*Artur Jasinski*) CROSSREFS Cf. A125866-A125878. Sequence in context: A125875 A059245 A268753 * A136065 A234102 A234104 Adjacent sequences:  A125873 A125874 A125875 * A125877 A125878 A125879 KEYWORD nonn AUTHOR Artur Jasinski, Dec 13 2006 EXTENSIONS Edited by Don Reble, Apr 24 2007 STATUS approved

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Last modified April 16 10:36 EDT 2021. Contains 343036 sequences. (Running on oeis4.)