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

Author

Artur Jasinski, Dec 13 2006

Keywords

• nonn

Crossrefs

Cf. A125866-A125878.

Programs

Mathematica

Do[If[Take[FactorInteger[EulerPhi[2n+1]][[ -1]],1]=={11} && PrimeQ[2n+1],Print[2n+1]],{n,1,10000}] (*Artur Jasinski*)

Extensions

Edited by Don Reble, Apr 24 2007