login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..57.

MATHEMATICA

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

CROSSREFS

Cf. A125866-A125878.

Sequence in context: A183203 A321680 A215667 * A216075 A253197 A255064

Adjacent sequences:  A125871 A125872 A125873 * A125875 A125876 A125877

KEYWORD

nonn

AUTHOR

Artur Jasinski, Dec 13 2006

EXTENSIONS

Edited by Don Reble, Apr 24 2007

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 16 03:28 EDT 2019. Contains 328040 sequences. (Running on oeis4.)