login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A139095 Fibonacci numbers whose sum of proper divisors is also a Fibonacci number. 2
1, 1, 2, 3, 5, 13, 89, 233, 1597, 28657, 514229, 433494437, 2971215073, 99194853094755497, 1066340417491710595814572169, 19134702400093278081449423917 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Numbers n such that A001065(n) is a Fibonacci number.

Comment from R. J. Mathar, Sep 17 2009: Certainly this contains 1 and the terms of A005478. Does it contain any other terms?

A001065(a(n)) is a Fibonacci number.

LINKS

Table of n, a(n) for n=1..16.

MAPLE

isA000045 := proc(n) local i, f ; for i from 0 do f := combinat[fibonacci](i) ; if f = n then RETURN(true) ; elif f > n then RETURN(false) ; fi ; od; end: A001065 := proc(n) numtheory[sigma](n)-n ; end: isA139095 := proc(n) RETURN( isA000045(n) and isA000045(A001065(n)) ) ; end: for i from 1 to 230 do if isA139095(combinat[fibonacci](i)) then printf("%d, ", combinat[fibonacci](i)) ; fi ; od: # R. J. Mathar, May 22 2008

CROSSREFS

Cf. A000045, A001065, A139589, A005478.

Sequence in context: A074691 A139589 A152114 * A005478 A117740 A041047

Adjacent sequences:  A139092 A139093 A139094 * A139096 A139097 A139098

KEYWORD

more,nonn

AUTHOR

Omar E. Pol, May 11 2008

EXTENSIONS

More terms from R. J. Mathar, May 22 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 21 05:01 EST 2017. Contains 294988 sequences.