%I

%S 1,2,4,2428957

%N Index of factorial primes of form n!+1.

%F a(n)=PrimePi[A002981(n)!+1]

%e exact subscript of 5th prime [1+27!=10888869450418352160768000001] not yet available

%Y A002981, A002982, A055490.

%K hard,nonn

%O 0,2

%A _Labos Elemer_, Jul 11 2001