If we are to believe best-selling novelist Anne Rice,
vampires resemble humans in many respects, but live secret lives hidden
among the rest of us mortals. Consider a numerical metaphor for
vampires. I call numbers like 2187 vampires numbers because they're
formed when two progenitor numbers 27 and 81 are multiplied together
(27*81 = 2187).
Note that the vampire, 2187, contains the same digits as both parents,
except that these digits are subtly hidden, scrambled in some fashion.
Similarly, 1435 is a vampire number because it contains the
digits of the progenitors 35 and 41.
(35*41=1435)
These vampire numbers secretly inhabit our number system, but most have
been undetected so far. I believe there are only six four-digit
vampires in existence, but have no idea if there are any larger vampire
numbers.
What is the largest vampire number you can find lurking out there in
the world of integers?
As the numbers get larger and larger, how often do you expect to find
vampires? Do they get sparser or more frequent as one searches for
vampires up to a googol?
I will be happy to report the largest vampire number ever found
in an article I'm writing.
(If you do any computer searches, could you tell me what language
you used and what machine you used and any other interesting
features?)
>Title: Cliff Puzzle 20: Vampire Numbers
>From: cl...@watson.ibm.com
>
>
>Vampire Numbers
>These vampire numbers secretly inhabit our number system, but most have
>been undetected so far. I believe there are only six four-digit
>vampires in existence, but have no idea if there are any larger vampire
>numbers.
I think that none of them have been detected because no one wanted to
bother to find them, this is something that would require doing
a whole lot of multiplication, and is probably better suited
to a computer.
The four-digit vampyres are ...
15 x 93 = 1395
21 x 60 = 1260
21 x 87 = 1827
27 x 81 = 2187
30 x 51 = 1530
35 x 41 = 1435
80 x 86 = 6880
Now this is only if we are strict and exclude
vampyres like
03 x 501 = 1503
03 x 510 = 1530
...
I would be tempted to include them, but the zero does leave
a question unanswered. Besides including them would
make the list of 4 digit vamps bigger than would be nice
to post to this group.
>
>What is the largest vampire number you can find lurking out there in
>the world of integers?
>
So far this, I guess I could find a bigger one if I tried hard enough.
50000 x 50219 = 2510950000
50000 x 51002 = 2550100000
50000 x 51020 = 2551000000
50000 x 51263 = 2563150000
50000 x 51902 = 2595100000
50000 x 52631 = 2631550000
50000 x 59021 = 2951050000
50000 x 59102 = 2955100000
65049 x 65244 = 4244056956
65132 x 65408 = 4260153856 /* largest possible with 32bit int...
and no I don't feel like codeing
multiple precision right now :) */
>As the numbers get larger and larger, how often do you expect to find
>vampires? Do they get sparser or more frequent as one searches for
>vampires up to a googol?
I find that near 2^32 they become very infrequent compared to
the density at small values (1 - 10000).
>
>I will be happy to report the largest vampire number ever found
>in an article I'm writing.
>
>(If you do any computer searches, could you tell me what language
>you used and what machine you used and any other interesting
>features?)
I used a C program. I just wrote it. Boy I gotta lay off the coffee!!!
The Machine is a 32bit Intel-based UNIX machine.
I didn't bother to optimize for speed, but it does a decent job
of finding vamps anyway.
If you are interested in my code, or how I coded it,
email cai...@vampyre.colorado.edu
^^^^^^^ I thought that was appropriate, don't you?
--
car...@vampyre.colorado.edu | What do 7, 11, and 4882195 have in
common? Send a self-addressed stamped envelope to 'PRIMES, PO BOX 17986,
Boulder, CO 80308, for your official prime number. Inquire within.
> 65049 x 65244 = 4244056956
> 65132 x 65408 = 4260153856 /* largest possible with 32bit int...
> and no I don't feel like codeing
> multiple precision right now :) */
65132 x 65408 = 4260153856
65132 x 87071 = 5671108372
65132 x 89402 = 5822931064
65133 x 98496 = 6415339968
and so on.
Maybe I didn't understand the rules correctly, but it seems to me
that once you have generated vampyre numbers you can get
arbitrarily large vampyre numbers with them.
If a and b are two numbers, each written with n digits, such that
a*b is written as a permutation of the digits of a and b, then
(a*10^m) * (b*10^m) will again be a vampyre number, since
you can write it with the digits of a*10^M and b*10^M. You write
a*b and then add 2m zeroes, with by an amazing coincidence are the
number of zeroes you have added to a and b together.
======================================================================
"It's not denial. I'm just very selective about
what I accept as reality."
--- Calvin ("Calvin and Hobbes")
======================================================================
Arturo Magidin
mag...@uclink.berkeley.edu
mag...@math.berkeley.edu
>Maybe I didn't understand the rules correctly, but it seems to me
>that once you have generated vampyre numbers you can get
>arbitrarily large vampyre numbers with them.
I am not sure who's rules you are following. Perhaps you can
post again and tell us all that 2 + 2 still equals 4 even for
extrodinarily large values of 2.
c'mon I think that the fun is in finding numbers of distinction.
Did you know that 1 approximated to ten decimal places is
1.0000000000 ?
Give us all a break.
--
car...@vampyre.colorado.edu | What do 7, 11, and 438479857 have in
Ok, here's the original post:
-------------------------BEGIN QUOTED ARTICLE----------------------------------
From cl...@watson.ibm.com Mon May 2 14:06:56 PDT 1994
Article: 71190 of sci.math
Path: agate!howland.reston.ans.net!EU.net!Germany.EU.net!Munich.Germany.EU.net!ibm.de!aixssc.uk.ibm.com!watnews.watson.ibm.com!watson.ibm.com!cliff
From: cl...@watson.ibm.com (cliff)
Newsgroups: sci.math
Subject: Vampire Numbers
Date: 28 Apr 1994 20:43:10 GMT
Organization: A
Lines: 43
Distribution: world
Message-ID: <2pp74u$g...@watnews1.watson.ibm.com>
NNTP-Posting-Host: cliff.watson.ibm.com
Title: Cliff Puzzle 20: Vampire Numbers
From: cl...@watson.ibm.com
Vampire Numbers
If we are to believe best-selling novelist Anne Rice,
vampires resemble humans in many respects, but live secret lives hidden
among the rest of us mortals. Consider a numerical metaphor for
vampires. I call numbers like 2187 vampires numbers because they're
formed when two progenitor numbers 27 and 81 are multiplied together
(27*81 = 2187).
Note that the vampire, 2187, contains the same digits as both parents,
except that these digits are subtly hidden, scrambled in some fashion.
Similarly, 1435 is a vampire number because it contains the
digits of the progenitors 35 and 41.
(35*41=1435)
These vampire numbers secretly inhabit our number system, but most have
been undetected so far. I believe there are only six four-digit
vampires in existence, but have no idea if there are any larger vampire
numbers.
What is the largest vampire number you can find lurking out there in
the world of integers?
As the numbers get larger and larger, how often do you expect to find
vampires? Do they get sparser or more frequent as one searches for
vampires up to a googol?
-------------------------END QUOTED MATERIAL-------------------------
Of course I agree that the only interest is in finding
non-trivially large vampyre numbers. Please point out the exact
place in this post were it is asked that the two numbers we
are multyplying together must not be both multiples of 10, or that
we must factor out as many powers of 10 as possible from both numbers.
Once you do that, I'll be happy to give you a break.
My point was that the definition of vampyre number is lacking unless
you specify that the trivial way of extending vampyre numbers which
I pointed out is ruled out.
Happy now?