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Search: id:A121938
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| 19, 421, 10039, 95383574161, 2384331073699, 1925929944387235853055979210606894889560480247048440342330377620014353281101
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OFFSET
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1,1
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COMMENT
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Corresponding numbers n such that (3^n + 5^n)/8 is prime are listed in A122853[n] = {3,5,7,17,19,109,509,661,709,1231,...}. All these numbers are primes. - Alexander Adamchuk (alex(AT)kolmogorov.com), Sep 14 2006
The next term is too large to include. - Alexander Adamchuk (alex(AT)kolmogorov.com), Sep 14 2006
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FORMULA
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a(n) = (A122853(n)^3 + A122853(n)^5)/8. a(n) = A074606[A122853(n)]/8 = A081186[A122853(n)]/4. a(n) = A079773[A122853(n)]. - Alexander Adamchuk (alex(AT)kolmogorov.com), Sep 14 2006
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MATHEMATICA
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Do[f=5^n+3^n; If[PrimeQ[f/2^3], Print[{n, f/2^3}]], {n, 1, 1231}] - Alexander Adamchuk (alex(AT)kolmogorov.com), Sep 14 2006
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CROSSREFS
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Cf. A074706, A122853, A081186, A079773, A121824, A121877, A005058, A005059, A121938, A109347.
Adjacent sequences: A121935 A121936 A121937 this_sequence A121939 A121940 A121941
Sequence in context: A069612 A077716 A089573 this_sequence A108145 A114350 A012506
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Sep 10 2006
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EXTENSIONS
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More terms from Alexander Adamchuk (alex(AT)kolmogorov.com), Sep 14 2006
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