A125874 Numbers k such that p=22*k+1 is prime and cos(2*Pi/p) is an algebraic number of an 11-smooth degree, but not 7-smooth.

1, 3, 4, 9, 15, 16, 18, 21, 28, 30, 33, 40, 45, 60, 64, 66, 81, 96, 99, 105, 108, 121, 135, 144, 150, 154, 165, 168, 175, 189, 198, 210, 225, 240, 243, 250, 288, 294, 324, 336, 343, 378, 396, 420, 448, 450, 490, 495, 525, 528, 550, 616, 625, 640, 675, 700, 726

Offset: 1

Author

Artur Jasinski, Dec 13 2006

Keywords

• nonn

Comments

Numbers k such that p=22*k+1 is prime and the greatest prime divisor of p-1 is 11.

Crossrefs

Cf. A125866-A125878.

Programs

Mathematica

Do[If[Take[FactorInteger[EulerPhi[22n+1]][[ -1]],1]=={11} && PrimeQ[22n+1],Print[n]],{n,1,10000}]

Extensions

Edited by Don Reble, Apr 24 2007