A124083 Numbers k such that prime(k)!/prime(k)# + 1 is prime.

1, 2, 3, 60, 90

Offset: 1

Author

Pierre CAMI, Nov 25 2006

Keywords

• nonn
• more

Comments

a(6) > 500 if it exists. - Felix Fröhlich, Sep 15 2019

a(6) > 2500 if it exists. - Michael S. Branicky, Oct 01 2024

Examples

			1*2/2 +1 = 2 prime so a(1)=1 as 2=prime(1).
1*2*3/(2*3) +1 = 2 prime so a(2)=2 as 3=prime(2).
1*2*3*4*5/(2*3*5) +1 = 5 prime so a(3)=3 as 5=prime(3).
		

Crossrefs

Cf. A092435 (p!/p#), A124082.

Programs

PARI

isok(k) = isprime(prime(k)!/prod(i=1, k, prime(i)) + 1); \\ Michel Marcus, Sep 15 2019