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A125856
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a(n) = least number k such that k^(2^n)+1, k^(2^n)+3, k^(2^n)+7 and k^(2^n)+9 are all prime.
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0
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OFFSET
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0,1
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COMMENTS
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In 1958, Schinzel showed that for each n>0, there are infinitely many primes among the numbers k^(2^n)+{1,3,7, or 9}.
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REFERENCES
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Sierpinski, W. Elementary theory of numbers. Warszawa 1964 Monografie Matematyczne Vol. 42.
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LINKS
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Table of n, a(n) for n=0..5.
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PROG
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(PARI) a(n) = {k = 1; while(!isprime(k^(2^n)+1) || !isprime(k^(2^n)+3) || !isprime(k^(2^n)+7) || !isprime(k^(2^n)+9), k++); k; } \\ Michel Marcus, Nov 03 2013
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CROSSREFS
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Cf. A125855, A057015, A125779, A125780.
Sequence in context: A118202 A277578 A089331 * A057110 A073275 A309528
Adjacent sequences: A125853 A125854 A125855 * A125857 A125858 A125859
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski, Dec 12 2006
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EXTENSIONS
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Edited by Don Reble, Dec 16 2006
One more term from Farideh Firoozbakht, Jan 01 2007
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STATUS
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approved
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