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Topic: Simple random number generator?
Replies: 8   Last Post: Dec 12, 2012 12:01 AM

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David Bernier

Posts: 3,729
Registered: 12/13/04
Re: Simple random number generator?
Posted: Dec 1, 2012 8:56 PM
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On 12/01/2012 07:21 PM, Christopher J. Henrich wrote:
> In article <>, Dr J
> R Stockton <> wrote:

>> In sci.math message <50b6cabe$0$24749$>, Wed, 28 Nov 2012
>> 21:38:34, Existential Angst <> posted:

>>> So are the digits of pi random or not?

>> The digits of pi are not random, because, unless the base is changed,
>> they are the same every time and can be defined relatively briefly, even
>> without assuming a definition of pi (which pi may formally lack).
>> But any arbitrarily chosen sub-sequence of the digits of pi will, I
>> believe, pass an appropriate proportion of the usual tests for
>> randomness. Note that the full expansion of the digits of pi contains
>> as sub-sequences of a given length all possible digit strings of that
>> length, some of which will not look random to the untutored eye, such as
>> yours.
>> A real mathematician could put that more precisely.

> If the digits of a number are uniformly distributed, so that in the
> (infinitely) long run 0's, 1's, 2's, etc. occur equally often, then the
> number is said to be "simply normal" (in base 10). If, for every k =
> 1,2, ..., all possible groups of k digits occur equally often in the
> long run, then the number is said to be "normal." (Reference: Hardy and
> Wright, /The/ /Theory/ /of/ /Numbers/ , Fourth ed., pp. 124-5.)
> Most of the irrational numbers that are interesting (such as sqrt(2) or
> pi) appear to be normal. Numbers that are not normal include all
> rational numbers, and some particular values of theta functions (for
> instance 0.1001000010000001 ... ).
> I think most mathematicians are of the *opinion* that pi is normal. But
> as far as I know, nobody has proved that it is, nor that it isn't. A
> frustrating situation. Part of the difficulty seems to be that the
> property of normality does not seem to be connected to other
> interesting properties of an irrational number.

Another question, this time on approximability by rational
numbers, can be asked for pi, for example.

Thm.: There are infinitely many pairs (m, n) of
positive integers such that

| pi - m/n | < 1/(n^2).

if 1/(n^2) is replaced by 1/(n^d), for a given real number
d >=2, one has the question:

Is it true that there are infinitely many pairs (m, n) of
positive integers such that
| pi - m/n | < 1/(n^d) ?

If d > 7.61, it is known to be false

Salikhov, 2008:


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