Prime related questions

[xordan]

Hello:
You wrote:
"Also, I was surprised to find that this seq wasn't already in the OEIS:
 n such that 10^n + prime(n) is prime..."

The sequence A125148, of which I am the  author, was modified by Klaus
Brockhaus so that it could remain in OEIS, but originally that sequence was
the following one:

Prime Numbers  that p = (10^x*z)+Y  where Y  it is an odd number prime  or
composite not divisible for 5  and x is equal or bigger that the quantity of
ciphers of Y.

Originally I deduced it for the  odd composites  , in way of demonstrating
that for any combination of ciphers that they finish in 1,3,7, or 9 it is
possible to find a prime number  adding a power of 10 equal or bigger than
the  ciphers cuantity  of Y multiplied for  a number bigger than 0.
Example:
9 are the first odd  composite number but 10^1*1+9=19
21 are the second odd  composite number (not divisible for 5) but
10^2*4+21=421
27 are the third add composite (not divisible for 5)  but 10^2*1+27=127.
etc..
In:
http://primes.utm.edu/curios/page.php?number_id=6894&submitter=Xordan
http://primes.utm.edu/curios/page.php?number_id=6983&submitter=Xordan
you find the numbers:
28123456789
The first prime number ending with all the ciphers (1 to 9) in order, and:
212345678987654321
The first prime number ending with all the ciphers (1 to 9 to 1) in
palindromic order.

 These numbers were obtained form that algorithm, besides other curiosities
that I have not remitted like:
11987654321234567879
The first prime  number ending with all the ciphers (9 to 1 to 9) in
palindromic order.
Hope you find some resemblance...
Greetings

XORDAN
Original in spanish, translated bysoftware
.2007/6/3, Jason Earls <jcearls at cableone.net>:
>
> Dear Seqfans,
>
> I recently found these twin probable primes:
>
> 2357*2^7532+105525
> 2357*2^7532+105527
> (2271 digits)
>
> Anyone know of databases that keep track of these? They shouldn't be in
> the
> OEIS, should they?
>
> Also, I was surprised to find that this seq wasn't already in the OEIS:
>
> n such that 10^n + prime(n) is prime.
> 2,4,27,63,756,899,
>
> I used PFGW to check up to 8000 and didn't find anymore.
>
> Worth submitting?
>
> Regards,
> Jason
> ======
> Check out my novel, Red Zen:
> http://tinyurl.com/2ylpml
>
>
>
>


-- 
xordan at hotmail.com
xordan_co at yahoo.com
xordan.tom at gmail.com
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