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A128335
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Numbers k such that (4^k + 5^k)/9 is prime.
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31
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5, 7, 19, 29, 61, 137, 883, 1381, 1823, 5227, 25561, 29537, 300893
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OFFSET
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1,1
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COMMENTS
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All terms are primes.
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LINKS
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MATHEMATICA
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k=4; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
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PROG
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CROSSREFS
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KEYWORD
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hard,more,nonn
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AUTHOR
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EXTENSIONS
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New term 300893 found by Jean-Louis Charton in November 2011 corresponding to a probable prime with 210315 digits.
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STATUS
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approved
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