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

 

Logo

Invitation: celebrating 50 years of OEIS, 250000 sequences, and Sloane's 75th, there will be a conference at DIMACS, Rutgers, Oct 9-10 2014.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A004169 Values of n for which a regular polygon with n sides cannot be constructed with ruler and compass. 4
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; text; internal format)
OFFSET

1,1

COMMENTS

Numbers m for which phi(a(m)) is not a power of 2, phi = A000010, Euler's totient function. - Reinhard Zumkeller, Jul 31 2012

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.

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.

MATHEMATICA

Select[ Range[75], !IntegerQ[ Log[2, EulerPhi[#] ] ]& ] (* Jean-Fran├žois Alcover, Nov 24 2011, after A003401 *)

PROG

(Haskell)

a004169 n = a004169_list !! (n-1)

a004169_list = map (+ 1) $ elemIndices 0 $ map a209229 a000010_list

-- Reinhard Zumkeller, Jul 31 2012

CROSSREFS

Cf. A003401 (complement).

Cf. A000010, A209229.

Sequence in context: A108815 A161992 A167377 * A066669 A059808 A020742

Adjacent sequences:  A004166 A004167 A004168 * A004170 A004171 A004172

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane, Branislav Kisacanin (bkisacan(AT)eecs.uic.edu)

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified October 1 14:07 EDT 2014. Contains 247511 sequences.