[seqfan] Re: Wrong formula in A091050

Neil Sloane njasloane at gmail.com
Wed Apr 29 03:09:47 CEST 2020


I agree with Robert Israel
Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com



On Tue, Apr 28, 2020 at 1:32 PM <israel at math.ubc.ca> wrote:

> The author of that formula seems to have forgotten that there could be
> perfect powers divisible by more than one prime. I think any "repair"
> would
> have very little resemblance to the current formula. My suggestion would
> be
> to delete.
>
> Cheers,
> Robert
>
> On Apr 28 2020, Ami Eldar wrote:
>
> >Dear SeqFans,
> >
> >The first formula in A091050 (Number of divisors of n that are perfect
> >powers.) is wrong:
> >a(n) = A073093(n)-A001221(n) = A001222(n)-A001221(n)+1.
> >(the 2nd equals sign is correct).
> >
> >This formula is wrong for the values of n = 36, 72, 100, 108, 144, 180,...
> >E.g. 36 has 4 divisors that are perfect powers 1, 4, 9, 36,
> >yet A001222(36)-A001221(36)+1 = 4 - 2 + 1 = 3.
> >
> >My question is whether this formula is repairable, or should it be
> deleted?
> >
> >Thanks,
> >Amiram
> >
> >--
> >Seqfan Mailing list - http://list.seqfan.eu/
> >
> >
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>



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