"Werner D. Sand" wrote:

>

> Let seq(p) = 23571113171923...p

> seq(2) = 2 = prime

> seq(3) = 23 = prime

> seq(7) = 2357 = prime

>

> Is there any p > 7 for which seq(p) is prime? I tried up to p = 223.

>

> Werner

Well, I have a small archive of posts to the group before the group was

moved to yahoo, and this was brought up before, here was the highest

that anyone on the list (at that time) came up with:

On Mon, 24 Apr 2000 Brian Schroeder wrote:

> Well, prime_cat(2,719) is prime with 355 digits and prime_cat(2,1033) > is prime with 499 digits and prime_cat(2,2297) is prime with 1171 > digits and prime_cat(2,3037) is prime with 1543 digits.

And then we got another excelent result from Marcel Martin who wrote:

On Tue, 25 Apr 2000 Marcel Martin wrote:

> Hello all,

>

> Sorry for my last mail. I gave the same infos than Brian Schroeder.

> I received his mail after having sent mine :(

>

> Well, I let my PC run all day long. All numbers from > prime_cat(2,3041) to prime_cat(2,11923) are composite.

>

> prime_cat(2,11927) is a strong pseudoprime for the bases 2, 3, 5,

> 7 and 11. This number has 5719 decimal digits.

>

> Marcel Martin

Where we defined prime_cat(x,y) to be the concatenation of all primes

from x to y, inclusively. I'd be curious to know, has anyone done any

more work on this since then?

-David C.