login
A125874
Numbers n such that p=22n+1 is prime and cos(2pi/p) is an algebraic number of an 11-smooth degree, but not 7-smooth.
1
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
1,2
COMMENTS
Numbers n such that p=22n+1 is prime and the greatest prime divisor of p-1 is 11.
MATHEMATICA
Do[If[Take[FactorInteger[EulerPhi[22n+1]][[ -1]], 1]=={11} && PrimeQ[22n+1], Print[n]], {n, 1, 10000}] (*Artur Jasinski*)
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Dec 13 2006
EXTENSIONS
Edited by Don Reble, Apr 24 2007
STATUS
approved