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A242041
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Number of k >= 1 that make n + k! and n - k! both prime.
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1
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0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 2, 0, 2, 0, 1, 0, 0, 1, 1, 0, 1, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 2, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 2, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0
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OFFSET
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1,35
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COMMENTS
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LINKS
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MAPLE
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a:= n -> nops(select(k -> isprime(n+k!) and isprime(n-k!),
[$1 ..min(numtheory:-factorset(n))-1])):
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PROG
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(PARI)
a(n)=c=0; for(k=1, n, if(ispseudoprime(n+k!)&&ispseudoprime(n-k!), c++)); return(c)
vector(100, n, a(n))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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