A166342 Numbers n such that (n+2)*n!*Sum((-1)^k/k!),k=0..n+2 is prime.

2, 3, 4, 8, 13, 42, 64, 166, 573, 1711

Offset

1,1

Comments

No further terms up to n=20000. The sequence a[n]=(n+2)*n!*Sum((-1)^k/k!),k=0..n+2 is A000255.

Links

Table of n, a(n) for n=1..10.

Formula

n is an index of the sequence a[n]=(n+2)*n!*Sum((-1)^k/k!),k=0..n+2 such that a[n] is prime.

Example

For n=3, a[3]=11 which is prime.

Prog

(PARI) z_even=1; z_odd=1;
for(n=1, 20000,
if(n%2==1,
z_odd=(n+2)*(n-1)*z_odd+1; if((ispseudoprime(z_odd)), print(n="n)),
z_even=(n+2)*(n-1)*z_even-1; if((ispseudoprime(z_odd)), print(n="n))); );

Crossrefs

Cf. A000255 (corresponding sequence).

Sequence in context: A361722 A092075 A091415 * A361502 A091816 A266400

Adjacent sequences: A166339 A166340 A166341 * A166343 A166344 A166345

Keyword

nonn

Author

Mike Oakes, Oct 12 2009

Status

approved