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

1,1

Comments

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

Links

Table of n, a(n) for n=1..22.

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.

Example

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

Crossrefs

Cf. A081710, A081711, A081713.

Sequence in context: A284623 A139490 A030375 * A178663 A084395 A047291

Adjacent sequences: A081709 A081710 A081711 * A081713 A081714 A081715

Keyword

nonn,more,hard

Author

Mike Oakes, Apr 04 2003

Extensions

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

Offset corrected by Sean A. Irvine, Sep 18 2023

Status

approved