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A160773
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Numbers k such that 3^k + 5^k + 7^k is prime.
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4
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0, 2, 10, 14, 24, 26, 126, 514, 522, 1658, 13758, 77194
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OFFSET
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1,2
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COMMENTS
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Note that k must be even.
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REFERENCES
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Joao Carlos Leandro da Silva, The Rainbow of Primes, Freund Publishing House, Tel Aviv, 2009.
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LINKS
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EXAMPLE
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For k=2 we obtain f(2) = 3^2 + 5^2 + 7^2 = 83 which is a prime.
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MAPLE
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MATHEMATICA
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Select[Range[0, 1000], PrimeQ[3^# + 5^# + 7^#] &] (* Wesley Ivan Hurt, Sep 19 2014 *)
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PROG
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(PARI) isok(n) = isprime(3^n + 5^n + 7^n) \\ Michel Marcus, Jul 25 2013
(Python)
def A160773_gen(): # generator of terms
p3, p5, p7 = [1]*3
for k in count(0):
if isprime(p3+p5+p7): yield k
p3 *= 3
p5 *= 5
p7 *= 7
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CROSSREFS
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KEYWORD
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nice,nonn,more
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AUTHOR
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Joao Carlos Leandro da Silva (zxawyh66(AT)yahoo.com), May 26 2009, Jun 01 2009
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EXTENSIONS
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STATUS
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approved
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