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 to 

•  find all primes of the form n!k+/-1 where 2<=k<=25 up to one that is at least 100000 digits.

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 194000 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

Discoverer Statistics

• 21/01/2012  Rene Dohmen proves 502051!7+1 (digits: 377722) prime (new multifactorial record)

• 18/01/2012 Nathan Russell provides stats on primality of number of the form n!10 +2

• 07/01/2012 Michael Lau proves 538508!23+1 (digits:124022), 544677!23+1 (digits:125560), 562746!23+1 (digits:130072) and 571312!23+1 (digits:132214) prime

• 19/09/2011 Rene Dohmen proves 478253!7+1  (digits: 358376)  prime (new multifactorial record)

• 21/07/2011 Matt Mills proves 257274!23-1 (digits: 55665) prime

• 06/06/2011 Rene Dohmen proves 446236!7-1  (digits: 332466)  prime (new multifactorial record)

• 27/05/2011 Nathan Russell uses Primo to certify 4213!6-2 prime

• 19/02/2011 Michael Lau proves 505855!23+1 (digits: 115904), 509171!23+1 (digits: 116727),  509332!23+1  (digits : 116767), 514285!23+1  (digits: 117996) and  521043!23+1  (digits: 119675) prime

• 26/01/2011 Rene Dohmen proves 368851!7-1 (digits: 270453)  prime (new multifactorial record)

• 18/12/2011 Rene Dohmen proves 364899!7+1 (digits: 267312) & 366923!7+1  (digits: 268920) prime (new multifactorial record)

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	502051	577722	Rene Dohmen	primes
n!7-1	446236	446236	Rene Dohmen	primes
n!8+1	140760	61535	Kimmo Herranen	primes
n!8-1	100000	54736	Kimmo Herranen	primes
n!9+1	110000	55341		primes
n!9-1	110000	51361		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	150000	58678		primes
n!12-1	250000	90296		primes
n!13+1	150000	52550		primes
n!13-1	150000	52097		primes
n!14+1	200000	60898		primes
n!14-1	200000	68950		primes
n!15+1	170000	54285		primes
n!15-1	190000	58486		primes
n!16+1	210000	62306		primes
n!16-1	170000	50089		primes
n!17+1	210000	59700		primes
n!17-1	200000	55782		primes
n!18+1	270000	72962		primes
n!18-1	210000	56421		primes
n!19+1	200000	50037		primes
n!19-1	220000	56410		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	77214	Masataka Oita (319773) ?	primes
n!21-1	280000	65282		primes
n!22+1	240000	53347		primes
n!22-1	240000	53527		primes
n!23+1	573021	132214	Michael Lau	primes
n!23-1	257274	55665	Matt Mills	primes
n!24+1	300000	59104		primes
n!24-1	300000	64262		primes
n!25+1	260000	51334		primes
n!25-1	260000	51554		primes
n!+/-1	70000+	+107707 -142891	Various	primes

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

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