A062701 Index of factorial primes of the form k! + 1.

1, 2, 4, 2428957

Offset: 1

Author

Labos Elemer, Jul 11 2001

Keywords

• hard
• nonn
• more

Examples

			The exact subscript of the 5th prime [1 + 27! = 10888869450418352160768000001] is not yet available.
		

Crossrefs

Cf. A000720, A002981, A002982, A055490, A088332.

Formula

a(n) = PrimePi(A002981(n)!+1).

Extensions

Offset 1 from Michel Marcus, Aug 29 2019