Status of Search for Multifactorial Primes

For further information on  multifactorial primes please see Chris Caldwell's glossary page on Multifactorial Primes
This site continues the work of Ray Ballinger.

The MultiF project's, which started in 2003 aims at finding all primes of the form n!k+/-1 where 2<=k<=25

•  up to 10000*type for each n.  
•  a prime with at least 50000 digits for each n.

To participate 

• email me, Ken Davis, at "kraDenken(at)yahoo(dot)com(dot)au" and reserve a type
• use multisieve to sieve a range of n (to eliminate those with small factors)
• use pfgw to find prps and prove primality
• Submit your prime to Chris Caldwell's The Prime Pages if big enough (Currently over 142000 digits) 
• Send me the Brillhart-Lehmer-Selfridge proof of primality output from pfgw
• I will add the (digits:nnnnn) and incorporate the data into the site

MultiF's position by number of Primes found
MultiF's position by score for Primes found

• 07/02/2010 Michael Lau proves 417240!23+1 (digits: 94083) prime

• 28/01/2010 Matt Mills finishes !23-1 to 230000 finding 9 additional primes including 229345!23-1 (digits: 49125)

• 18/01/2010 Ken Davis finishes !22-1 to 220000 ==> all types complete up to 10000*type.  

• 07/01/2010 Matt Mills Proves 171232!23-1 (digits: 35733), 172344!23-1 (digits: 35986) and 177871!23-1(digits: 37246) prime

• 01/01/2010 Matt Mills proves 166332!23-1 (digits: 34619) prime

• 31/12/2009 Matt Mills proves 200379!23-1 (digits: 42410) prime

• 23/12/2009 Matt Mills reserves !23-1 type

• 26/09/2009 Rene Dohmen proves 208502!7+1 (digits 145502) prime (new multifactorial record)

• 31/08/2009 Rene Dohmen proves 190453!7-1 (digits: 131837) and 206494!7+1 (digits: 143977) prime

• 14/08/2009 Michael Lau proves 382722!23+1 (digits: 85676) prime

Earlier news items

Recent changes are in Red

Type	nmaxtested	Digits*	Searcher	primes
n!2+1	100000	112762		primes
n!2-1	100000	93343		primes
n!3+1	100000	144697		primes
n!3-1	110000	84173	Andrea Pacini	primes
n!4+1	120000	58508	Don Routman	primes
n!4-1	120000	51252	Don Routman	primes
n!5+1	100000	69090		primes
n!5-1	100000	77730		primes
n!6+1	100000	75339		primes
n!6-1	100000	64524		primes
n!7+1	208502	145502	Rene Dohmen	primes
n!7-1	190453	131837	Rene Dohmen	primes
n!8+1	140760	61535	Kimmo Herranen	primes
n!8-1	100000	54736	Kimmo Herranen	primes
n!9+1	100000	46520		primes
n!9-1	100000	49304		primes
n!10+1	120000	50053		primes
n!10-1	120000	50001		primes
n!11+1	275259	124096	Ken Davis	primes
n!11-1	275259	125257	Ken Davis	primes
n!12+1	120000	43013		primes
n!12-1	120000	41435		primes
n!13+1	150000	52550		primes
n!13-1	150000	52097		primes
n!14+1	145200	47569		primes
n!14-1	200000	68950		primes
n!15+1	150000	43867		primes
n!15-1	150000	46186		primes
n!16+1	160000	43117		primes
n!16-1	160000	45370		primes
n!17+1	170000	46924		primes
n!17-1	170000	46817		primes
n!18+1	180000	46361		primes
n!18-1	180000	46900		primes
n!19+1	200000	50037		primes
n!19-1	200000	49615		primes
n!20+1	200000	73102	Masataka Oita (290700) 250001+	primes
n!20-1	200000	72521	Masataka Oita (288574) 250001+	primes
n!21+1	212048	49402	Masataka Oita (319773) ?	primes
n!21-1	210000	41387		primes
n!22+1	220000	47541		primes
n!22-1	220000	43162	Ken Davis	primes
n!23+1	417305	90783	Michael Lau	primes
n!23-1	230000	49125	Matt Mills	primes
n!24+1	240000	47047		primes
n!24-1	240000	48575		primes
n!25+1	250000	46619		primes
n!25-1	250000	47337		primes
n!+/-1	30000+	+107707 -142891	Various	primes

* Number of digits in the largest known prime of this form

Multifactorial primes of a different flavour n!k+/-2