login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A071387 Smallest number for which InvPhi-Set has 2n-1 entries. 1
0, 2, 8, 32, 40, 48, 396, 704, 72, 216, 144, 1056, 360, 384, 1320, 240, 9000, 7128, 480, 1296, 15936, 3072, 864, 7344, 720, 4992, 2016, 6000, 4752, 3024, 9984, 1920, 7560, 22848, 29160, 3360, 13248, 27720, 9072, 9360, 4032, 4800, 16896, 3840, 9504, 23520, 5040 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..47.

FORMULA

a(n)=Min{x; Card[InvPhi[x]]=2n-1}; a(1)=0 because of Carmichael conjecture

EXAMPLE

2n-1=13:Min{396,400,420,552,560,660}=396=a(7)

CROSSREFS

Cf. A000010, A014197, A058277, A063512, A071386-A071389.

Sequence in context: A279692 A332444 A323145 * A330782 A200063 A238984

Adjacent sequences:  A071384 A071385 A071386 * A071388 A071389 A071390

KEYWORD

nonn

AUTHOR

Labos Elemer, May 23 2002

EXTENSIONS

a(12)-a(47) from Donovan Johnson, Jul 27 2011

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 February 26 09:44 EST 2020. Contains 332277 sequences. (Running on oeis4.)