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Search: id:A121170
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| A121170 |
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Largest prime divisor of Fibonacci[5n]. |
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+0
2
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| 5, 11, 61, 41, 3001, 61, 141961, 2161, 109441, 3001, 474541, 2521, 14736206161, 141961, 230686501, 3041, 3415914041, 109441, 67735001, 570601, 8288823481, 474541, 2441738887963981, 20641, 158414167964045700001, 14736206161
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Except from a(1) = 5 all a(n) are congruent to 1, Mod 10 (final digit is 1). Final digit of most prime divisors of F(5n) is 1.
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EXAMPLE
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a(2) = 11 because F(10)= 5 * 11.
a(4) = 41 because F(20)= 3 * 5 * 11 * 41.
a(10) = 3001 because F(50)= 5^2 * 11 * 101 * 151 * 3001.
a(25) = 158414167964045700001 because F(125)= 5^3 * 3001 * 158414167964045700001.
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MATHEMATICA
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Table[Max[Flatten[FactorInteger[Fibonacci[5n]]]], {n, 1, 50}]
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CROSSREFS
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Cf. A000045.
Sequence in context: A057822 A095150 A041697 this_sequence A101209 A050568 A065555
Adjacent sequences: A121167 A121168 A121169 this_sequence A121171 A121172 A121173
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KEYWORD
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nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Aug 14 2006
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