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A004169
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Values of n for which a regular polygon with n sides cannot be constructed with ruler and compass.
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3
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7, 9, 11, 13, 14, 18, 19, 21, 22, 23, 25, 26, 27, 28, 29, 31, 33, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 65, 66, 67, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 86, 87, 88, 89, 90, 91
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 183.
C. F. Gauss, Disquisitiones Arithmeticae, 1801. English translation: Yale University Press, New Haven, CT, 1966, p. 460.
B. L. van der Waerden, Modern Algebra. Unger, NY, 2nd ed., Vols. 1-2, 1953, Vol. 1, p. 187.
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LINKS
| T. D. Noe, Table of n, a(n) for n = 1..1000
C. F. Gauss, Disquisitiones Arithmeticae, Lipsiae, 1801. Reprinted in C. F. Gauss, Werke, 1863.
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MATHEMATICA
| Select[ Range[75], !IntegerQ[ Log[2, EulerPhi[#] ] ]& ] (* From Jean-François Alcover, Nov 24 2011, after A003401 *)
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CROSSREFS
| Cf. A003401.
Sequence in context: A108815 A161992 A167377 * A066669 A059808 A020742
Adjacent sequences: A004166 A004167 A004168 * A004170 A004171 A004172
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KEYWORD
| nonn,nice,changed
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Branislav Kisacanin (bkisacan(AT)eecs.uic.edu)
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