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


%S 1,2,2016,3226,8130

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

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

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

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

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

%Y Cf. A000522 (corresponding sequence).

%K nonn

%O 1,2

%A _Mike Oakes_, Oct 12 2009

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Last modified July 1 20:10 EDT 2022. Contains 354975 sequences. (Running on oeis4.)