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Search: id:A082387
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| A082387 |
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Numbers n such that (5^n + 2^n)/7 is prime. |
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25
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| 3, 17, 19, 47, 101, 1709, 2539, 5591, 6037, 8011, 19373, 26489, 27427
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Next term > 35000. - Giovanni Resta (g.resta(AT)iit.cnr.it), Apr 06 2006
For (2^n + 5^n)/7 to be a prime n should be a prime too. - Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 06 2007
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LINKS
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Primeform, User group for PFGW and PrimeForm programs
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EXAMPLE
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a(1)=3 because (5^3+2^3)/7=(125+8)/7=19 is prime.
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MATHEMATICA
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Do[f=(2^n+5^n)/7; If[PrimeQ[f], Print[{n, f}]], {n, 1, 35000}] - Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 06 2007
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CROSSREFS
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Cf. A057469 = numbers n such that (2^n + 3^n)/5 is prime.
Adjacent sequences: A082384 A082385 A082386 this_sequence A082388 A082389 A082390
Sequence in context: A019342 A029473 A103088 this_sequence A032923 A018750 A077778
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KEYWORD
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more,nonn
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AUTHOR
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Hugo Pfoertner (hugo(AT)pfoertner.org), May 22 2003
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EXTENSIONS
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More terms from Hugo Pfoertner (hugo(AT)pfoertner.org), Jun 23 2003
More terms from Giovanni Resta (g.resta(AT)iit.cnr.it), Apr 06 2006
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