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A166342 Numbers n such that (n+2)*n!*Sum((-1)^k/k!),k=0..n+2 is prime. 0
2, 3, 4, 8, 13, 42, 64, 166, 573, 1711 (list; graph; refs; listen; history; text; internal format)
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: A186272 A092075 A091415 * A091816 A266400 A274914

Adjacent sequences:  A166339 A166340 A166341 * A166343 A166344 A166345

KEYWORD

nonn

AUTHOR

Mike Oakes, Oct 12 2009

STATUS

approved

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Last modified May 16 15:56 EDT 2022. Contains 353706 sequences. (Running on oeis4.)