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%I #5 Oct 19 2017 03:15:05
%S 1,3,4,9,15,16,18,21,28,30,33,40,45,60,64,66,81,96,99,105,108,121,135,
%T 144,150,154,165,168,175,189,198,210,225,240,243,250,288,294,324,336,
%U 343,378,396,420,448,450,490,495,525,528,550,616,625,640,675,700,726
%N 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.
%C Numbers n such that p=22n+1 is prime and the greatest prime divisor of p-1 is 11.
%t Do[If[Take[FactorInteger[EulerPhi[22n+1]][[ -1]],1]=={11} && PrimeQ[22n+1],Print[n]],{n,1,10000}] (*Artur Jasinski*)
%Y Cf. A125866-A125878.
%K nonn
%O 1,2
%A _Artur Jasinski_, Dec 13 2006
%E Edited by _Don Reble_, Apr 24 2007