Prime related questions

[Robert Israel]

Please note that the usual term in English is "digits",
not "ciphers".

Cheers,
Robert Israel

On Sun, 3 Jun 2007, xordan wrote:

> 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
>