A076679 Numbers k such that 3*k! + 1 is prime.

2, 3, 4, 6, 7, 9, 10, 13, 23, 25, 32, 38, 40, 47, 96, 3442, 4048, 4522, 4887, 7033, 9528, 12915, 31762, 114482

Offset: 1

Author

Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 25 2002

Keywords

• nonn
• more

Comments

a(25) > 115000. - Serge Batalov, Jun 15 2025

Examples

			k = 6 is here because 3*6! + 1 = 2161 is prime.
		

Crossrefs

Cf. A002981, A051915, A076680, A076681, A076682, A076683, A178488, A180626, A126896.

Programs

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 05 2020

Extensions

More terms from Serge Batalov, Feb 18 2015

a(20)-a(23) from Roger Karpin, Nov 13 2016

a(24) from Serge Batalov, Jun 15 2025