On August 29 1995, Harvey Dubner and Harry Nelson discovered
seven
consecutive primes in arithmetic progression, namely *p*, *p* +
210, *p* + 420, *p* + 630, *p* + 840, *p* + 1050 and
*p* + 1260 where *p* is the 97-digit number:

1089533431247059310875780378922957732908036492993138195385213105561742150447308967213141717486151.

On 7 November 1997, we - Harvey Dubner, Tony Forbes, Nik Lygeros, Michel Mizony and Paul Zimmermann - announced the discovery of eight consecutive primes in arithmetic progression after a search lasting a couple of months using a variety of PC's and Unix workstations.

We then initiated a search for nine primes, calling on the help of about a
hundred people world-wide and using about 200 computers. On 15 January 1998,
this search ended successfully when **Manfred Toplic** of Klagenfurt,
Austria, found nine consecutive primes in arithmetic
progression using Tony's program CP09.EXE on a PC.

**References:**

Harvey Dubner and Harry Nelson, "Seven primes in arithmetic progression",
*Mathematics of Computation*, October 1997. Also available as a
postscript file.

Harvey Dubner, Tony Forbes and Paul Zimmermann, "8 consec. primes in AP",
*NMBRTHRY*,
November 1997.

Harvey Dubner, Tony Forbes, Nik Lygeros, Michel Mizony and Paul Zimmermann, "9
consecutive primes in arithmetic progression",
*NMBRTHRY*,
January 1998.

Richard K. Guy, *Unsolved Problems in Number Theory*, Springer-Verlag,
1994, 2nd edition, Section A.6.

Paulo Ribenboim, *The New Book of Prime Number Records*,
Springer-Verlag, 1995, 3rd edition, Section IV.C.

**E-mail addresses:**

Harvey Dubner <HDubner1@compuserve.com>

Tony Forbes <tonyforbes@ltkz.demon.co.uk>

Michel Mizony <mizony@desargues.univ-lyon1.fr>

Nik Lygeros <lygeros@desargues.univ-lyon1.fr>

Paul Zimmermann <paul.zimmermann@loria.fr>