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!)
A129293 Numbers m such that m^4-1 has no divisors d with 1<d<m-1. 4
3, 4, 6, 150, 180, 240, 270, 420, 570, 1290, 1320, 2310, 2550, 2730, 3360, 3390, 4260, 4650, 5850, 5880, 6360, 6780, 9000, 9240, 9630, 10530, 10890, 11970, 13680, 13830, 14010, 14550, 16230, 16650, 18060, 18120, 18540, 19140, 19380, 21600, 21840, 23370 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A129292(a(n)) = #{1, a(n)-1} = 2.

Essentially the same as A070155, since m^4-1=(m-1)(m+1)(1+m^2). - R. J. Mathar, Jun 14 2008

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

{1,5,7,35,37,185,259,1295} is the set of divisors of 6^4-1, therefore 6 is a term, A129292(6) = #{1,3} = 2.

CROSSREFS

Cf. A129295, A129297.

Sequence in context: A267943 A066466 A332511 * A233512 A095877 A024476

Adjacent sequences:  A129290 A129291 A129292 * A129294 A129295 A129296

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Apr 09 2007

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 July 7 23:03 EDT 2020. Contains 335502 sequences. (Running on oeis4.)