

A125867


Numbers n such that p=6n+1 is prime and cos(2pi/p) is an algebraic number of a 3smooth degree, but not 2smooth.


3



1, 2, 3, 6, 12, 16, 18, 27, 32, 72, 81, 96, 128, 192, 216, 243, 432, 486, 576, 648, 1728, 2048, 2916, 3072, 6561, 8748, 23328, 24576, 34992, 55296, 78732, 104976, 124416, 131072, 139968, 165888, 196608, 248832, 294912, 331776, 442368, 839808
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OFFSET

1,2


COMMENTS

Numbers n such that p=6n+1 is prime and the greatest prime divisor of p1 is 3.


LINKS

Table of n, a(n) for n=1..42.


MATHEMATICA

Do[If[Take[FactorInteger[EulerPhi[6n+1]][[ 1]], 1]=={3} && PrimeQ[6n+1], Print[n]], {n, 1, 100000}]


CROSSREFS

Cf. A024899, A058383, A125866A125878.
Sequence in context: A124485 A200175 A286906 * A032727 A323392 A174801
Adjacent sequences: A125864 A125865 A125866 * A125868 A125869 A125870


KEYWORD

nonn


AUTHOR

Artur Jasinski, Dec 13 2006


EXTENSIONS

Edited by Don Reble, Apr 24 2007


STATUS

approved



