[seqfan] Re: vampire numbers: multiple-vampire numbers?
Tanya Khovanova
mathoflove-seqfan at yahoo.com
Thu Dec 25 23:01:40 CET 2008
Check this sequence out:
A014575 Vampire numbers (numbers having more than one pair of fangs are
listed once for each pair).
I think the definition should explicitly state if we are talking about
two fangs or more fangs here.
Another confusing sequence:
A014575 Vampire numbers (numbers having more than one pair of fangs are
listed once for each pair).
This sequence looks like vampire numbers with exactly two fangs in
different way (word "one pair"), then why 1395 is here? I continue to
be confused.
--- zak seidov <zakseidov at yahoo.com> wrote:
> Hello Tanya and all you SeqFans,
>
> 1395 is the first non-trivial double-vampire number
> with two valid factorizations:
> 1395=15*93=5*9*31.
>
> What about other non-trivial double-vampire numbers?
>
> I call trivial multiple-vampire numbers those ending with zero's:
> 1260=6*210=21*60,
> 13950=>{15, 930}, {93, 150}, {5, 9, 310}, {5, 31, 90}, {9, 31, 50}.
>
> Again, what about non-trivial multiple-vampire numbers?
>
> Happy New, 2009!
>
> zak
>
>
> --- On Thu, 12/25/08, Tanya Khovanova <mathoflove-seqfan at yahoo.com>
> wrote:
>
> > From: Tanya Khovanova <mathoflove-seqfan at yahoo.com>
> > Subject: [seqfan] vampire numbers
> > To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
> > Date: Thursday, December 25, 2008, 2:18 PM
> > Hello SeqFans,
> >
> > I just wrote an essay about problems with names for vampire
> > numbers:
> > http://blog.tanyakhovanova.com/?p=89
> >
> > I suggest renaming the corresponding sequences. For example
> > we might
> > want to name:
> > A080718 Numbers n such that all the digits of the prime
> > factors of n
> > exactly match the digits of n.
> > --- prime-fanged vampire numbers.
> >
> > A014575 Vampire numbers (numbers having more than one pair
> > of fangs are
> > listed once for each pair).
> > --- double symmetrical fangs vampire numbers.
> >
> > A020342 Vampire numbers: n has a factorization using
> > n's digits (e.g.
> > 1395 = 31*9*5).
> > --- we might keep the name or call them generalized vampire
> > numbers.
> >
> > I didn't check if all the sequences I mention in my
> > essay are in the
> > OEIS. I would like to clean the naming conventions first,
> > then someone
> > can add more sequences if desired.
> >
> > Best, Tanya
> >
> >
> >
> > _______________________________________________
> >
> > Seqfan Mailing list - http://list.seqfan.eu/
>
>
>
>
>
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