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Search: id:A139589
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| A139589 |
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Fibonacci numbers with Fibonacci number of divisors. |
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+0
5
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| 1, 1, 2, 3, 5, 13, 89, 233, 610, 987, 1597, 10946, 28657, 514229, 3524578, 9227465, 24157817, 39088169, 63245986, 433494437, 1836311903, 2971215073, 7778742049, 20365011074, 591286729879, 4052739537881, 17167680177565, 44945570212853
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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A000005(a(n)) is a Fibonacci number.
For the terms shown here the number of divisors is 1 or 2 or 8. - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 12 2008
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MAPLE
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A000045 := proc(n) option remember ; coeftayl( x/(1-x-x^2), x=0, n) ; end: isA000045 := proc(n) local a; for a from 0 do if A000045(a) > n then RETURN(false) ; elif A000045(a)=n then RETURN(true) ; fi ; od: end: A000005 := proc(n) numtheory[tau](n) ; end: isA139589 := proc(n) RETURN(isA000045(n) and isA000045(A000005(n))) ; end: for i from 1 to 130 do a000045 := A000045(i) ; if isA139589(a000045) then printf("%d, ", a000045) ; fi ; od: - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 11 2008
with(combinat): with(numtheory): F:={seq(fibonacci(k), k=1..100)}: a:=proc(n) if member(tau(fibonacci(n)), F)=true then fibonacci(n) else end if end proc: seq(a(n), n=1..70); - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 12 2008
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CROSSREFS
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Cf. A000005, A000045, A063375, A133021, A134805.
Adjacent sequences: A139586 A139587 A139588 this_sequence A139590 A139591 A139592
Sequence in context: A056162 A001685 A074691 this_sequence A139095 A005478 A117740
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KEYWORD
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nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), May 09 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric Deutsch (deutsch(AT)duke.poly.edu), May 11 2008
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