Search: id:A139095
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%I A139095
%S A139095 1,1,2,3,5,13,89,233,1597,28657,514229,433494437,2971215073,
%T A139095 99194853094755497,1066340417491710595814572169,
%U A139095 19134702400093278081449423917
%N A139095 Fibonacci numbers whose sum of proper divisors is also a Fibonacci number.
%C A139095 Numbers n such that A001065(n) is a Fibonacci number.
%C A139095 Comment from R. J. Mathar, Sep 17 2009: Certainly this contains 1 and 
               the terms of A005478. Does it contain any other terms?
%C A139095 A001065(a(n)) is a Fibonacci number.
%p A139095 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 (mathar(AT)strw.leidenuniv.nl), 
               May 22 2008
%Y A139095 Cf. A000045, A001065, A139589, A005478.
%Y A139095 Sequence in context: A074691 A139589 A152114 this_sequence A005478 A117740 
               A041047
%Y A139095 Adjacent sequences: A139092 A139093 A139094 this_sequence A139096 A139097 
               A139098
%K A139095 more,nonn
%O A139095 1,3
%A A139095 Omar E. Pol (info(AT)polprimos.com), May 11 2008
%E A139095 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 22 2008

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