A081712 Numbers k such that k! - k# + 1 is prime, where k# is the primorial function.

4, 6, 7, 8, 10, 20, 21, 26, 101, 119, 172, 409, 621, 1043, 1204, 1283, 1673, 2003, 4336, 5773, 12913, 13517

Offset: 1

Author

Mike Oakes, Apr 04 2003

Keywords

• nonn
• more
• hard

Comments

Some of the larger entries may only correspond to probable primes.

Examples

			a(1)=4 because 4!-4#+1=19 is prime
		

Links

• Mike Oakes, Primo-factorials.
• Mike Oakes, Primo-factorials, message 12028 in primenumbers Yahoo group, Apr 3, 2003. [Cached copy]
• Joe McLean, Interesting Sources of Probable Primes.

Crossrefs

Cf. A081710, A081711, A081713.

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

Offset corrected by Sean A. Irvine, Sep 18 2023