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A086122
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Primes of the form (5^k-1)/4.
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7
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31, 19531, 12207031, 305175781, 177635683940025046467781066894531, 14693679385278593849609206715278070972733319459651094018859396328480215743184089660644531, 35032461608120426773093239582247903282006548546912894293926707097244777067146515037165954709053039550781
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OFFSET
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1,1
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COMMENTS
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Corresponding exponents k are listed in A004061. - Alexander Adamchuk, Jan 23 2007
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LINKS
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Table of n, a(n) for n=1..7.
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FORMULA
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a(n) = (5^A004061(n) - 1)/4 = A003463[ A004061(n) ]. - Alexander Adamchuk, Jan 23 2007
A003464 INTERSECT A000040.
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MATHEMATICA
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Do[f=(5^n-1)/4; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1000}] (* Alexander Adamchuk, Jan 23 2007 *)
Select[(5^Range[300]-1)/4, PrimeQ] (* Harvey P. Dale, Dec 11 2016 *)
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CROSSREFS
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Cf. A000668, A076481.
Cf. A003463, A004061, A074479.
Sequence in context: A161395 A215610 A292009 * A239167 A263585 A176349
Adjacent sequences: A086119 A086120 A086121 * A086123 A086124 A086125
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KEYWORD
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nonn
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AUTHOR
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Labos Elemer, Jul 23 2003
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EXTENSIONS
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More terms from Alexander Adamchuk, Jan 23 2007
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STATUS
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approved
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