A125873 Prime numbers n such that cos(2pi/n) is an algebraic number of an 11-smooth degree, but not 7-smooth.

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

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