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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
OFFSET
1,1
COMMENTS
Subsequence of the complement of (A239321 union A125163).
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
Derek Orr, Aug 12 2014
STATUS
approved