A242040 Numbers n such that n + k! and n - k! are both prime for some k.

4, 5, 6, 9, 11, 12, 13, 15, 17, 18, 21, 23, 25, 29, 30, 35, 37, 39, 42, 43, 45, 47, 53, 55, 60, 65, 67, 69, 72, 73, 77, 81, 83, 85, 95, 99, 102, 103, 105, 107, 108, 111, 113, 125, 127, 129, 131, 133, 137, 138, 143, 145, 149, 150, 151, 155, 157, 161, 163, 165, 173, 175, 180, 185, 187

Offset

1,1

Comments

Subsequence of the complement of (A239321 union A125163).

Links

Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

Example

5 + 2! = 7 and 5 - 2! = 3 are both prime. Thus 5 is a member of this sequence.

Prog

(PARI)
a(n)=for(k=1, n, if(ispseudoprime(n+k!)&&ispseudoprime(n-k!), return(k)))
n=1; while(n<500, if(a(n), print1(n, ", ")); n++)

Crossrefs

Cf. A239321, A125163, A241425, A245716.

Sequence in context: A075903 A029942 A162016 * A206822 A195993 A334457

Adjacent sequences: A242037 A242038 A242039 * A242041 A242042 A242043

Keyword

nonn

Author

Derek Orr, Aug 12 2014

Status

approved