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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A089684 Numbers n such that 2*phi(n) > n. 2
1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..63.

FORMULA

Asymptotic to c*n with c=2.045...

MATHEMATICA

lst={}; Do[If[2*EulerPhi[n]>n, AppendTo[lst, n]], {n, 200}]; lst (* T. D. Noe *)

Select[ Range[130], 2EulerPhi[ # ] > # &] (* Robert G. Wilson v, Jan 16 2004 *)

CROSSREFS

Cf. A036798, A067800 (composite n such that 2 phi(n) > n).

Cf. A036798, the missing odd numbers.

Sequence in context: A176271 A144396 A060747 * A283002 A105356 A082453

Adjacent sequences:  A089681 A089682 A089683 * A089685 A089686 A089687

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jan 16 2004

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified September 23 21:16 EDT 2017. Contains 292391 sequences.