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A125874
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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.
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0
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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; internal format)
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OFFSET
| 1,2
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COMMENTS
| Numbers n such that p=22n+1 is prime and the greatest prime divisor of p-1 is 11.
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MATHEMATICA
| Do[If[Take[FactorInteger[EulerPhi[22n+1]][[ -1]], 1]=={11} && PrimeQ[22n+1], Print[n]], {n, 1, 10000}] (*Artur Jasinski*)
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CROSSREFS
| Cf. A125866-A125878.
Sequence in context: A054162 A174783 A183203 * A165921 A030136 A054188
Adjacent sequences: A125871 A125872 A125873 * A125875 A125876 A125877
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KEYWORD
| nonn
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AUTHOR
| Artur Jasinski (grafix(AT)csl.pl), Dec 13 2006
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EXTENSIONS
| Edited by Don Reble (djr(AT)nk.ca), Apr 24 2007
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