login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A289690 Least k such that there are exactly n perfect powers between 10k and 10k + 10. 0
5, 1, 2, 12, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
I do not know if a(5) exists. If it does, the numbers 10k+1, 10k+3, 10k+5, 10k+7, 10k+9 will be perfect powers. But those numbers are very scarce.
Further, a(6), ..., a(10) cannot exist because of the Mihailescu theorem, as the only adjoining perfect powers are 8 and 9.
a(5) is extremely unlikely to exist; if it does, it is larger than 10^70. - Charles R Greathouse IV, Jul 21 2017
LINKS
EXAMPLE
If n=2, then there are 2 power numbers between 20 and 30: 25 and 27, and this is the least k with this property.
PROG
(PARI) a(n)=my(k=0); while(sum(j=10*k+1, 10*k+9, (j==1) || ispower(j)) !=n, k++); k; \\ Michel Marcus, Jul 20 2017
CROSSREFS
Sequence in context: A226613 A274989 A328199 * A088781 A085608 A258339
KEYWORD
nonn,fini
AUTHOR
Wolfram Hüttermann, Jul 09 2017
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 24 04:32 EST 2024. Contains 370288 sequences. (Running on oeis4.)