A166339 Numbers n such that Sum(n!/k!),k=0..n is prime.

1, 2, 2016, 3226, 8130

Offset: 1

Author

Mike Oakes, Oct 12 2009

Keywords

• nonn

Comments

No further terms up to n=20000. The sequence a[n]=Sum(n!/k!),k=0..n is A000522.

Examples

			For n=2, a[2]=5 which is a prime.
		

Crossrefs

Cf. A000522 (corresponding sequence).

Programs

PARI

a=1;for(n=1,20000,a=n*a+1;if(ispseudoprime(a,0),print("n="n)));

Formula

n is an index of the sequence a[n]=Sum(n!/k!),k=0..n such that a[n] is prime.