Newsgroups: rec.puzzles
From: hoey@AIC.NRL.Navy.Mil (Dan Hoey)
Date: 4 Aug 92 20:45:11 GMT
Subject: Prime of concatenated primes (spoiler)

che...@gsusgi1.gsu.edu (Parthasarathy Nambi) writes:

> 23, 235, 2357, 235711, etc   Do you see the pattern?
> In the above sequence 23 and 2357 are primes.  Actually
> 2357 is a fascinating prime (more about it later).
> I have continued this series of numbers upto the prime 103, and haven't
> found any other prime - if one can *believe* Mathematica's PrimeQ test.

according to Mathematica,

2,357,111,317,192,329,313,741,434,753,596,167,717,379,838,997,101,-
  103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,-
  191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,-
  277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,-
  379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,-
  467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,-
  587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,-
  677,683,691,701,709,719

is the next prime in the sequence.

Dan Hoey
Hoey@AIC.NRL.Navy.Mil