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Search: id:A072556
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| A072556 |
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Numbers n such that n and the n-th Fibonacci number have the same number of distinct prime factors. |
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1
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| 1, 3, 4, 5, 7, 10, 11, 12, 13, 14, 17, 22, 23, 26, 29, 34, 43, 47, 83, 94, 131, 137, 359, 431, 433, 449, 509, 569, 571
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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a(7)=10 because 10 and 10th Fibonacci number(i.e. 55) have the same number of prime factors i.e. 2 - Shyam Sunder Gupta (guptass(AT)rediffmail.com), Feb 05 2006
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MAPLE
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with(combinat): with(numtheory): a:=proc(n) if nops(factorset(fibonacci(n)))=nops(factorset(n)) then n else fi end: seq(a(n), n=1..150); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 02 2006
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MATHEMATICA
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Insert[Select[Range[1, 50], Length[FactorInteger[ # ]] ==Length[FactorInteger[Fibonacci[ # ]]] &], 2, 2] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Mar 20 2006
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CROSSREFS
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Cf. A001221, A022307.
Sequence in context: A101760 A165713 A105148 this_sequence A047365 A048342 A030502
Adjacent sequences: A072553 A072554 A072555 this_sequence A072557 A072558 A072559
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KEYWORD
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more,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 06 2002
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EXTENSIONS
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More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 25 2003
Edited by R. J. Mathar, Aug 11 2008
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