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

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

Offset

1,3

Comments

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

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

Links

Table of n, a(n) for n=1..10.

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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A214842 A299517 A268660 * A264860 A061354 A162709

Adjacent sequences: A180624 A180625 A180626 * A180628 A180629 A180630

Keyword

nonn,more

Author

Robert G. Wilson v, Sep 13 2010

Extensions

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

Status

approved