primes in pi: 1, 2, 6, 38, 16208, 47577, 78073, ...

[Jonathan Post]

On the other hand, it would be more "natural" to do this in base e.

Picking another base almost at random from OEIS, we have pi base 8 digits

  A006941 <http://www.research.att.com/~njas/sequences/A006941> Expansion of
*Pi* in *base* 8.
and if we concatenate these and look at primality of these as if they were
decimal digits we get the primes:

3, 31, 311, 31103755242102643, ...

-- Jonathan Vos Post


On 7/17/06, Richard Guy <rkg at cpsc.ucalgary.ca> wrote:
>
> It would be more natural (??) to do this in base 2.
>
> So here are two new(?) sequences for people to
> check and extend:
>
> The first
>           2,  8,    14,    18,   ...
>
> digits in the binary representation of pi form the
> primes
>           3, 401, 25667, 410687, ...
>
> in decimal notation.        R.
>
> On Mon, 17 Jul 2006, Eric W. Weisstein wrote:
>
> > Anyone curious about prime number searches may be
> > (slightly) interested to learn that the concatenation
> > of the first 78073 digits of pi (including the initial
> > 3) forms a probable prime.  For the complete list of
> > known indices of primes in the digits of pi (as listed
> > above), see
> > http://www.research.att.com/~njas/sequences/A060421 .
> >
> > I believe at 78073 digits, pi(78073) becomes the 65th
> > largest known PRP (cf.
> > http://www.primenumbers.net/prptop/prptop.php).
> >
> > Cheers,
> > -Eric
> >
>
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