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 A139095 Fibonacci numbers whose sum of proper divisors is also a Fibonacci number. 2

%I

%S 1,1,2,3,5,13,89,233,1597,28657,514229,433494437,2971215073,

%T 99194853094755497,1066340417491710595814572169,

%U 19134702400093278081449423917

%N Fibonacci numbers whose sum of proper divisors is also a Fibonacci number.

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

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

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

%p 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

%Y Cf. A000045, A001065, A139589, A005478.

%K more,nonn

%O 1,3

%A _Omar E. Pol_, May 11 2008

%E More terms from _R. J. Mathar_, May 22 2008

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Last modified June 25 03:50 EDT 2019. Contains 324338 sequences. (Running on oeis4.)