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Search: id:A119588
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| A119588 |
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Numbers n such that the number of divisors of Fibonacci(n), tau(Fibonacci(n)), is not a perfect power of 2. |
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+0
1
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| 12, 24, 25, 36, 48, 50, 56, 60, 72, 75, 84, 91, 96, 100, 108, 110, 112, 120, 132, 144, 150, 153, 156, 168, 175, 180, 182, 192, 200, 204, 216, 220, 224, 225, 228, 240, 252, 264, 273, 275, 276, 280, 300, 306, 312, 324, 325, 330, 336, 342, 348, 350, 360, 364, 372
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Has many terms in common with A023172 (41 below 1000), but neither is a subsequence of the other since 125 is not in this sequence.
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LINKS
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Blair Kelly, Fibonacci and Lucas Factorizations.
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FORMULA
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a(n) = {k: tau(Fibonacci(k)) != 2^i for all i}.
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EXAMPLE
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F(12) = 144 has 15 divisors: {1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 36, 48, 72, 144}. Since 15 is not a power of 2, 12 is in the sequence.
F(24) = 46368 has 72 divisors. Since 72 is not a power of 2, 24 is in the sequence.
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MATHEMATICA
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Do[If[ !IntegerQ[Log[2, DivisorSigma[0, Fibonacci[n]]]], Print[n]], {n, 10^3}]
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CROSSREFS
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Adjacent sequences: A119585 A119586 A119587 this_sequence A119589 A119590 A119591
Sequence in context: A117320 A040132 A095780 this_sequence A065303 A108902 A126935
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KEYWORD
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nonn
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AUTHOR
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Ryan Propper (rpropper(AT)stanford.edu), Jun 01 2006
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