%N Duplicate of A066674.
%C Original name was: a(n) = the least number k such that cos(2pi/k) is an algebraic number of a prime(n)-smooth degree, but not prime(n-1)-smooth.
%C Comments from _N. J. A. Sloane_, Jan 07 2013 (Start)
%C This is a duplicate of A066674. This follows from the following argument. The degree of the minimal polynomial of cos(2pi/k) is phi(k)/2, where phi is Euler's totient function. Then a(n) is the least number k such that prime(n) is the largest prime dividing phi(k) and prime(n-1) does not divide phi(k)/2. For the rest of the proof see Bjorn Poonen's remarks in A066674.
%C It also seems likely that this is the same as A035095, but this is an open problem.
%C Conjecture: this sequence contains only primes (this would follow if this is indeed the same as A035095).
%D See A181877.
%Y Cf. A066674, A035095, A125866-A125877.
%A _Artur Jasinski_, Dec 13 2006
%E Edited by _Don Reble_, Apr 24 2007
%E Minor edits by _Ray Chandler_, Oct 20 2011