# [seqfan] Re: Wrong formula in A091050

Ami Eldar amiram.eldar at gmail.com
Wed Apr 29 08:59:39 CEST 2020

```Thank you. I have deleted the formula.

On Wed, Apr 29, 2020 at 4:10 AM Neil Sloane <njasloane at gmail.com> wrote:

> 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.
> 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/
> > >
> > >
> >
> > --
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> >
>
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>

```