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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 19 13:01 EDT 2019. Contains 328222 sequences. (Running on oeis4.)