A076134 Numbers k such that 3*k! - 1 is prime.

0, 1, 2, 3, 4, 5, 9, 12, 17, 26, 76, 379, 438, 1695, 6709, 13313, 18504, 19021, 24488, 45552, 49085, 65451

Offset: 1

Author

Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 30 2002

Keywords

• nonn
• more

Comments

a(23) > 80000. - Serge Batalov, Jun 09 2025

Examples

			k = 5 is here because 3*5! - 1 = 359 is prime.
		

Crossrefs

Cf. A051915, A076134.

Cf. A002982, A076133, A099350, A099351, A180627, A180628, A180629, A180630, A180631.

Programs

Maple

for n from 0 to 1000 do if isprime(3*n! - 1) then print(n) end if end do;

Mathematica

Select[Range[0, 10^3], PrimeQ[3 #! - 1] &] (* Robert Price, May 27 2019 *)

PARI

isok(n) = isprime(3*n! - 1); \\ Michel Marcus, Nov 13 2016

PFGW

ABC2 3*$a!+1
a: from 1 to 1000 // Jinyuan Wang, Feb 04 2020

Extensions

a(15)-a(21) from Roger Karpin, Nov 13 2016

a(22) from Serge Batalov, Jun 08 2025