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A262345
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Numbers k such that 4^k + 21 is prime.
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1
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2, 4, 8, 22, 24, 26, 98, 228, 246, 808, 1556, 1792, 1978, 3424, 69738, 108376, 169584
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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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EXAMPLE
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For k = 26, 4^26 + 21 = 4503599627370517 is prime.
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MATHEMATICA
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Select[Range[3000], PrimeQ[4^# + 21] &]
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PROG
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(Magma) [n: n in [0..700] | IsPrime(4^n+21)];
(PARI) for(n=1, 1e3, if(isprime(4^n+21), print1(n", "))) \\ Altug Alkan, Sep 18 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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STATUS
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approved
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