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A175235
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Prime p such that 2^p + 21 is also prime.
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1
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3, 5, 7, 11, 19, 61, 163, 911, 997, 16657, 36551
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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For p=3, 2^3+21=29; p=5, 2^5+21=53; p=7, 2^7+21=149.
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MATHEMATICA
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Select[Prime[Range[10000]], PrimeQ[(2^# + 21)] &] (* Vincenzo Librandi, Oct 04 2015 *)
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PROG
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(Magma) [p: p in PrimesUpTo(4000) | IsPrime(2^p+21) ]
(Perl) use ntheory ":all"; use Math::GMP qw/:constant/; forprimes { my $n = 2**$_+21; say if is_prime($n) } 20000; # Dana Jacobsen, Oct 03 2015
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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