A180627 Numbers k such that 6*k! - 1 is prime.

0, 1, 2, 5, 8, 42, 318, 326, 1054, 2987, 11243

Offset: 1

Author

Robert G. Wilson v, Sep 13 2010

Keywords

• nonn
• more

Comments

Tested to 4400. - Robert G. Wilson v, Sep 28 2010

a(11) > 6300. - Jinyuan Wang, Feb 04 2020

Links

• Index entries for sequences related to numbers of primes of the form k*n!+-1

Crossrefs

Cf. A002982, A076133, A076134, A099350, A099351, A180628, A180630, A180630, A180631.

Programs

Mathematica

fQ[n_] := PrimeQ[6 n! - 1]; k = 0; lst = {}; While[k < 1501, If[ fQ@k, AppendTo[lst, k]; Print@k]; k++ ]; lst

PARI

is(k) = ispseudoprime(6*k!-1); \\ Jinyuan Wang, Feb 04 2020

Extensions

a(10) from Robert G. Wilson v, Sep 28 2010

a(11) from Michael S. Branicky, Jul 04 2024