[seqfan] Re: Composite numbers n such that digits of prime factors of n are either 4 or 9.

Neil Sloane njasloane at gmail.com
Thu Sep 24 05:24:27 CEST 2020

Yes, I agree with Marc.

If someone has nothing better to do it is OK to make an index entry for
EXISTING sequences like "primes / composites whose digits are 4 and 9"
but don't add any more of the type.

Once you make a list, there is the temptation to "fill in the gaps", and to
create sequences for "primes / composites whose digits are 4 and 7".
If we have them already then it is ok to index them, but don't create any
new ones.

And don't start doing it in other bases.

On Wed, Sep 23, 2020 at 11:01 PM Marc LeBrun <mlb at well.com> wrote:

> >=israel at math.ubc.ca wrote:
> > More generally, for every list S of primes we could have a sequence for
> > "Composite numbers whose prime factors are in S".  There are lots of
> those!
> Indeed.  That idea's fine to address the naming issue, but let's please
> try to avoid encouraging a proliferation of pointless sequences!
> --
> Seqfan Mailing list - http://list.seqfan.eu/

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