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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 (list; graph; refs; listen; history; text; internal format)
 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 A010456 Adjacent sequences:  A242037 A242038 A242039 * A242041 A242042 A242043 KEYWORD nonn AUTHOR Derek Orr, Aug 12 2014 STATUS approved

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Last modified July 23 00:43 EDT 2019. Contains 325228 sequences. (Running on oeis4.)