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%I #13 Nov 01 2014 18:33:28
%S 1,2,3,5,8,13,21,34,55,89,233,377,610,987,1597,4181,6765,10946,17711,
%T 28657,75025,121393,196418,317811,514229,1346269,2178309,3524578,
%U 5702887,9227465,24157817,39088169,63245986,165580141,433494437
%N Deficient Fibonacci numbers.
%C Intersection of A000045 and A005100. - _Michel Marcus_, Nov 01 2014
%H Alois P. Heinz, <a href="/A074317/b074317.txt">Table of n, a(n) for n = 1..300</a>
%e a(9)=55 is a term because the sum of the aliquot divisors of 55 (which is a Fibonacci number), i.e., 1+5+11=17, is less than 55.
%t DeficientQ[n_]:=DivisorSigma[1,n]<2n;a={};Do[f=Fibonacci[n];If[DeficientQ[f],AppendTo[a,f]],{n,1,10^2,1}];a (* _Vladimir Joseph Stephan Orlovsky_, Jul 25 2008 *)
%t Select[Fibonacci[Range[50]],DivisorSigma[1,#]<2#&] (* _Harvey P. Dale_, Apr 28 2012 *)
%Y Cf. A000045 (Fibonacci), A005100 (deficient).
%K base,hard,nonn
%O 1,2
%A _Shyam Sunder Gupta_, Sep 22 2002
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