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Search: id:A118539
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| A118539 |
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Adjacent generalized Fermat primes. |
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+0
1
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| 3, 3, 3, 75, 113, 2163, 63739, 13221, 54809, 3656571, 6992033, 125441
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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David Broadhurst, Posting to PrimeForm list.
Yves Gallot's compilation of generalized Fermat primes.
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FORMULA
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a(n) is the smallest number such that (a(n)+1)^(2^n)+1 and (a(n)-1)^(2^n)+1 are both prime.
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EXAMPLE
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a(11)=6992033 because 6992034^2048+1 is prime, 6992032^2048+1 is prime and no smaller pair of bases differing by 2 gives a pair of primes with the exponent 2^11=2048.
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CROSSREFS
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Sequence in context: A025549 A135584 A091323 this_sequence A015665 A131462 A117032
Adjacent sequences: A118536 A118537 A118538 this_sequence A118540 A118541 A118542
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KEYWORD
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hard,nonn
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AUTHOR
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David Broadhurst (D.Broadhurst(AT)open.ac.uk), May 06 2006
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