[seqfan] Re: vampire numbers: multiple-vampire numbers?

[zak seidov]

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
> 
> 
> 
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