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A213073
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Numbers n such that (7^n - 4^n)/3 is prime.
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1
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OFFSET
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1,1
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COMMENTS
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All terms are primes.
Next term > 10^5.
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LINKS
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Table of n, a(n) for n=1..9.
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MATHEMATICA
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k=7; Do[p=Prime[n]; f=(k^p-4^p)/(k-4); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
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PROG
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(PARI) is(n)=ispseudoprime((7^n-4^n)/3) \\ Charles R Greathouse IV, Jun 13 2017
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CROSSREFS
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Cf. A128344, A128024, A059802.
Sequence in context: A140547 A131480 A262228 * A267527 A286453 A309375
Adjacent sequences: A213070 A213071 A213072 * A213074 A213075 A213076
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KEYWORD
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hard,more,nonn
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AUTHOR
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Robert Price, Jun 04 2012
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STATUS
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approved
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