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Search: id:A139590
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| A139590 |
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Fibonacci numbers with non-Fibonacci number of divisors. |
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+0
4
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| 8, 21, 34, 55, 144, 377, 2584, 4181, 6765, 17711, 46368, 75025, 121393, 196418, 317811, 832040, 1346269, 2178309, 5702887, 14930352, 102334155, 165580141, 267914296, 701408733, 1134903170, 4807526976, 12586269025, 32951280099
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A000005(a(n)) is a non-Fibonacci number A001690.
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EXAMPLE
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34 belongs to the sequence because the number of its divisors, 4, is not a Fibonacci number.
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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: isA139590 := proc(n) RETURN(isA000045(n) and not isA000045(A000005(n))) ; end: for i from 1 to 130 do a000045 := A000045(i) ; if isA139590(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(j), j=1..30)}: a:= proc(n) if member(tau(fibonacci(n)), F) = false then fibonacci(n) else end if end proc: seq(a(n), n=1..50); - Emeric Deutsch (deutsch(AT)duke.poly.edu)
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CROSSREFS
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Cf. A000005, A000045, A001690, A063375, A133021.
Sequence in context: A003249 A134862 A090206 this_sequence A154894 A000567 A124484
Adjacent sequences: A139587 A139588 A139589 this_sequence A139591 A139592 A139593
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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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