|
|
A242040
|
|
Numbers n such that n + k! and n - k! are both prime for some k.
|
|
1
|
|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
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
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|